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"rect"><img src="http://www.w3.org/Icons/w3c_home" alt="W3C" width=
"72" height="48" /></a>
<h1 class="notoc" id="title">Speech Recognition Grammar
Specification Version 1.0</h1>
</div>
<!-- W3C HEADER -->
<div class="head"><!-- DATE -->
<h2 class="notoc" id="pub-date">W3C Recommendation 16
March 2004</h2>
<dl>
<dt>This version:</dt>
<dd><a href=
"http://www.w3.org/TR/2004/REC-speech-grammar-20040316/">http://www.w3.org/TR/2004/REC-speech-grammar-20040316/</a></dd>
<dt>Latest version:</dt>
<dd><a href=
"http://www.w3.org/TR/speech-grammar/">http://www.w3.org/TR/speech-grammar/</a></dd>
<dt>Previous version:</dt>
<dd><a href=
"http://www.w3.org/TR/2003/PR-speech-grammar-20031218/">http://www.w3.org/TR/2003/PR-speech-grammar-20031218/</a></dd>
<dt>Editors:</dt>
<dd>Andrew Hunt, <span>ScanSoft</span></dd>
<dd>Scott McGlashan, <span>Hewlett-Packard</span></dd>
<dt>Contributors:</dt>
<dd>See <a href="#S6" shape="rect">Acknowledgements</a></dd>
</dl>

<p>Please refer to the <a href="http://www.w3.org/2004/03/speech-grammar-errata.html"><strong>errata</strong></a> for this document, which may include some normative corrections.</p>

<p>See also <a href="http://www.w3.org/2003/03/Translations/byTechnology?technology=speech-grammar"><strong>translations</strong></a>.</p>



<p class="copyright"><a href=
"http://www.w3.org/Consortium/Legal/ipr-notice#Copyright" shape=
"rect">Copyright</a> &copy; 2004 <a href="http://www.w3.org/" shape=
"rect"><acronym title=
"World Wide Web Consortium">W3C</acronym></a><sup>&reg;</sup>
(<a href="http://www.csail.mit.edu/" shape="rect"><acronym title=
"Massachusetts Institute of Technology">MIT</acronym></a>, <a href=
"http://www.ercim.org/" shape="rect"><acronym title=
"European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>,
<a href="http://www.keio.ac.jp/" shape="rect">Keio</a>), All Rights
Reserved. W3C <a href=
"http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer"
shape="rect">liability</a>, <a href=
"http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks"
shape="rect">trademark</a>, <a href=
"http://www.w3.org/Consortium/Legal/copyright-documents" shape=
"rect">document use</a> and <a href=
"http://www.w3.org/Consortium/Legal/copyright-software" shape=
"rect">software licensing</a> rules apply.</p>
<hr title="Separator from Header" /></div>
<h2 class="notoc" id="id1"><a id="abstract" name="abstract" shape=
"rect">Abstract</a></h2>
<p>This document defines syntax for representing grammars for use
in speech recognition so that developers can specify the words and
patterns of words to be listened for by a speech recognizer. The
syntax of the grammar format is presented in two forms, an
Augmented BNF Form and an XML Form. The specification makes the two
representations mappable to allow automatic transformations between
the two forms.</p>

<h2 class="notoc" id="id2">Status of this Document</h2>

<p><em>This section describes the status of this document at
the time of its publication. Other documents may supersede this
document. A list of current W3C publications and the latest
revision of this technical report can be found in the
<a href="http://www.w3.org/TR/">W3C technical reports index</a>
at http://www.w3.org/TR/.</em></p>

<p>This document has been reviewed by W3C Members and other
interested parties, and it has been endorsed by the Director
as a <a
href="http://www.w3.org/2004/02/Process-20040205/tr.html#RecsW3C">W3C
Recommendation</a>. W3C's role in making the Recommendation is to
draw attention to the specification and to promote its widespread
deployment. This enhances the functionaility and interoperability
of the Web.</p>

<p>This specification is part of the W3C Speech Interface Framework
and has been developed within the <a href="http://www.w3.org/Voice/">W3C Voice Browser Activity</a> (<a href="http://www.w3.org/Voice/Activity.html">activity statement</a>) by participants in
the <a href="http://www.w3.org/Voice/Group/">Voice Browser Working
Group</a> (<a href="http://cgi.w3.org/MemberAccess/AccessRequest">W3C
Members only</a>).</p>

<p>The design of SRGS 1.0 has been widely reviewed (see the
<a href="http://www.w3.org/TR/2003/PR-speech-grammar-20031218/disposition.html">
disposition of comments</a>) and satisfies the Working Group's
technical requirements.  A list of implementations is included in the
<a href="http://www.w3.org/Voice/2003/srgs-ir/">SRGS 1.0
implementation report</a>, along with the associated test suite.</p>



<p>Comments are welcome on <a
href="mailto:www-voice@w3.org">www-voice@w3.org</a> (<a
href="http://lists.w3.org/Archives/Public/www-voice/">archive</a>).
See <a href="http://www.w3.org/Mail/">W3C mailing list and archive usage
guidelines</a>.</p>

<p>The W3C maintains a list of <a
href="http://www.w3.org/2001/09/voice-disclosures.html">any patent
disclosures related to this work</a>.</p>


<!-- END OF W3C HEADER -->
<div>
<h2 class="notoc" id="id-S0"><a id="S0" name="S0" shape=
"rect">Table of Contents</a></h2>
<ul class="toc">
<li class="tocline">1. <a href="#S1" shape="rect">Introduction</a>
<ul class="toc">
<li class="tocline">1.1 <a href="#S1.1" shape="rect">Grammar
Processors and User Agents</a></li>
<li class="tocline">1.2 <a href="#S1.2" shape="rect">Scope</a></li>
<li class="tocline">1.3 <a href="#S1.3" shape="rect">Grammar
Conversions</a></li>
<li class="tocline">1.4 <a href="#S1.4" shape="rect">Semantic
Interpretation</a></li>
<li class="tocline">1.5 <a href="#S1.5" shape="rect">Embedded
Grammars</a></li>
<li class="tocline">1.6 <a href="#S1.6" shape=
"rect">Terminology</a></li>
</ul>
</li>
<li class="tocline">2. <a href="#S2" shape="rect">Rule
Expansions</a>
<ul class="toc">
<li class="tocline">2.1 <a href="#S2.1" shape=
"rect">Tokens</a></li>
<li class="tocline">2.2 <a href="#S2.2" shape="rect">Rule
References</a>
<ul class="toc">
<li class="tocline">2.2.1 <a href="#S2.2.1" shape="rect">Local
References</a></li>
<li class="tocline">2.2.2 <a href="#S2.2.2" shape="rect">External
Reference by URI</a></li>
<li class="tocline">2.2.3 <a href="#S2.2.3" shape="rect">Special
Rules</a></li>
<li class="tocline">2.2.4 <a href="#S2.2.4" shape=
"rect">Referencing N-gram Documents</a></li>
</ul>
</li>
<li class="tocline">2.3 <a href="#S2.3" shape="rect">Sequences and
Encapsulation</a></li>
<li class="tocline">2.4 <a href="#S2.4" shape=
"rect">Alternatives</a>
<ul class="toc">
<li class="tocline">2.4.1 <a href="#S2.4.1" shape=
"rect">Weights</a></li>
</ul>
</li>
<li class="tocline">2.5 <a href="#S2.5" shape="rect">Repeats</a>
<ul class="toc">
<li class="tocline">2.5.1 <a href="#S2.5.1" shape="rect">Repeat
Probabilities</a></li>
</ul>
</li>
<li class="tocline">2.6 <a href="#S2.6" shape="rect">Tags</a></li>
<li class="tocline">2.7 <a href="#S2.7" shape=
"rect">Language</a></li>
<li class="tocline">2.8 <a href="#S2.8" shape=
"rect">Precedence</a></li>
</ul>
</li>
<li class="tocline">3. <a href="#S3" shape="rect">Rule
Definitions</a>
<ul class="toc">
<li class="tocline">3.1 <a href="#S3.1" shape="rect">Basic Rule
Definition</a></li>
<li class="tocline">3.2 <a href="#S3.2" shape="rect">Scoping of
Rule Definitions</a></li>
<li class="tocline">3.3 <a href="#S3.3" shape="rect">Example
Phrases</a></li>
</ul>
</li>
<li class="tocline">4. <a href="#S4" shape="rect">Grammar
Documents</a>
<ul class="toc">
<li class="tocline">4.1 <a href="#S4.1" shape="rect">Grammar Header
Declarations</a></li>
<li class="tocline">4.2 <a href="#S4.2" shape="rect">ABNF
Self-Identifying Header</a></li>
<li class="tocline">4.3 <a href="#S4.3" shape="rect">XML Form
Prolog and Root Element</a></li>
<li class="tocline">4.4 <a href="#S4.4" shape="rect">Character
Encoding</a></li>
<li class="tocline">4.5 <a href="#S4.5" shape=
"rect">Language</a></li>
<li class="tocline">4.6 <a href="#S4.6" shape="rect">Mode</a></li>
<li class="tocline">4.7 <a href="#S4.7" shape="rect">Root
Rule</a></li>
<li class="tocline">4.8 <a href="#S4.8" shape="rect">Tag
Format</a></li>
<li class="tocline">4.9 <a href="#S4.9" shape="rect">Base URI</a>
<ul class="toc">
<li class="tocline">4.9.1 <a href="#S4.9.1" shape="rect">Resolving
Relative URIs</a></li>
</ul>
</li>
<li class="tocline">4.10 <a href="#S4.10" shape=
"rect">Pronunciation Lexicon</a></li>
<li class="tocline">4.11 <a href="#S4.11" shape="rect">Meta
Data</a>
<ul class="toc">
<li class="tocline">4.11.1 <a href="#S4.11.1" shape="rect">Meta and
HTTP-Equiv</a></li>
<li class="tocline">4.11.2 <a href="#S4.11.2" shape="rect">XML
Metadata (XML Only)</a></li>
</ul>
</li>
<li class="tocline"><span>4.12</span> <a href="#S4.12" shape=
"rect"><span>Tag</span></a></li>
<li class="tocline"><span>4.13</span> <a href="#S4.13" shape=
"rect">Comments</a></li>
<li class="tocline"><span>4.14</span> <a href="#S4.14" shape=
"rect">Grammar Fetching</a></li>
<li class="tocline"><span>4.15</span> <a href="#S4.15" shape=
"rect">ABNF Keywords</a></li>
</ul>
</li>
<li class="tocline">5. <a href="#S5" shape="rect">Conformance</a>
<ul class="toc">
<li class="tocline">5.1 <a href="#S5.1" shape="rect">Conforming XML
Form Grammar Fragments</a></li>
<li class="tocline">5.2 <a href="#S5.2" shape="rect">Conforming
Stand-Alone XML Form Document</a></li>
<li class="tocline">5.3 <a href="#S5.3" shape="rect">Using XML Form
Grammars with other Namespaces</a></li>
<li class="tocline">5.4 <a href="#S5.4" shape="rect">Conforming XML
Form Grammar Processors</a></li>
<li class="tocline">5.5 <a href="#S5.5" shape="rect">Conforming
Stand-Alone ABNF Form Grammar Documents</a></li>
<li class="tocline">5.6 <a href="#S5.6" shape="rect">Conforming
ABNF Form Grammar Processors</a></li>
<li class="tocline">5.7 <a href="#S5.7" shape="rect">Conforming
ABNF/XML Form Grammar Processors</a></li>
<li class="tocline">5.8 <a href="#S5.8" shape="rect">Conforming
User Agents</a></li>
</ul>
</li>
<li class="tocline">6. <a href="#S6" shape=
"rect">Acknowledgements</a></li>
</ul>
<ul class="toc">
<li class="tocline">Appendix A. <a href="#AppA" shape=
"rect">References</a>
<ul class="toc">
<li class="tocline">A.1 <a href="#AppA.1" shape="rect">Normative
References</a></li>
<li class="tocline">A.2 <a href="#AppA.2" shape="rect">Informative
References</a></li>
</ul>
</li>
<li class="tocline">Appendix B. <a href="#AppB" shape="rect">DTD
for XML Form Grammars</a> (Informative)</li>
<li class="tocline">Appendix C. <a href="#AppC" shape="rect">XML Schema Definition
For XML Form Grammars</a> (Normative)</li>
<li class="tocline">Appendix D. <a href="#AppD" shape="rect">Formal
Syntax for Augmented BNF Form Grammars</a> (Normative)</li>
<li class="tocline">Appendix E. <a href="#AppE" shape="rect">DTMF
Grammars</a> (Normative)</li>
<li class="tocline">Appendix F. <a href="#AppF" shape="rect">XSLT
Style Sheet to Convert XML Form Grammars to the ABNF Form</a>
(Informative)</li>
<li class="tocline">Appendix G. <a href="#AppG" shape="rect">Media
Types and File Suffix</a> (Informative)</li>
<li class="tocline">Appendix H. <a href="#AppH" shape=
"rect">Logical Parse Structure</a> (Informative)
<ul class="toc">
<li class="tocline">H.1 <a href="#AppH.1" shape="rect">Terminology
and Notation</a></li>
<li class="tocline">H.2 <a href="#AppH.2" shape="rect">Parsing Rule
References</a></li>
<li class="tocline">H.3 <a href="#AppH.3" shape=
"rect">Recursion</a></li>
</ul>
</li>
<li class="tocline">Appendix I. <a href="#AppI" shape=
"rect">Features under Consideration for Future Versions</a>
(Informative)</li>
<li class="tocline">Appendix J. <a href="#AppJ" shape=
"rect">Example Grammars in ABNF Form and XML Form</a> (Informative)
<ul>
<li class="tocline">J.1 <a href="#AppJ.1" shape="rect">Simple
Examples (English)</a></li>
<li class="tocline">J.2 <a href="#AppJ.2" shape=
"rect">Cross-Reference Examples (English)</a></li>
<li class="tocline">J.3 <a href="#AppJ.3" shape="rect">Korean
Examples</a></li>
<li class="tocline">J.4 <a href="#AppJ.4" shape="rect">Chinese
Examples</a></li>
<li class="tocline">J.5 <a href="#AppJ.5" shape="rect">Swedish
Examples</a></li>
</ul>
</li>
</ul>
<p><a id="S1" name="S1" shape="rect"></a></p>
<h2 id="id-S1">1. Introduction</h2>
<p>This document defines the syntax for grammar representation. The
grammars are intended for use by speech recognizers and other
<a href="#S1.1" shape="rect">grammar processors</a> so that
developers can specify the words and patterns of words to be
listened for by a speech recognizer.</p>
<p>The syntax of the grammar format is presented in two forms, an
<em>Augmented BNF</em> (ABNF) Form and an XML Form. The
specification ensures that the two representations are <a href=
"#S1.3" shape="rect">semantically mappable</a> to allow automatic
transformations between the two forms.</p>
<ul>
<li><em>Augmented BNF syntax (ABNF):</em> this is a plain-text
(non-XML) representation which is similar to traditional BNF
grammar and to many existing BNF-like representations commonly used
in the field of speech recognition including the JSpeech Grammar
Format <a href="#ref-jsgf" shape="rect">[JSGF]</a> from which this
specification is derived. Augmented BNF should not be confused with
Extended BNF which is used in DTDs for XML and SGML.<br clear=
"none" />
&nbsp;</li>
<li><em>XML:</em> This syntax uses XML elements to represent the
grammar constructs and adapts designs from the PipeBeach grammar,
TalkML <a href="#ref-talkml" shape="rect">[TALKML]</a> and a
research XML variant of the JSpeech Grammar Format <a href=
"#ref-jsgf" shape="rect">[JSGF]</a>.</li>
</ul>
<p>Both the ABNF Form and XML Form have the expressive power of a
Context-Free Grammar (CFG). A <a href="#S1.1" shape="rect">grammar
processor</a> that does not support recursive grammars has the
expressive power of a Finite State Machine (FSM) or regular
expression language. For definitions of CFG, FSM, regular
expressions and other formal computational language theory see, for
example, <a href="#ref-hu79" shape="rect">[HU79]</a>. This form of
language expression is sufficient for the vast majority of speech
recognition applications.</p>
<p>This W3C standard is known as the Speech Recognition Grammar
Specification and is modelled on the JSpeech Grammar Format
specification <a href="#ref-jsgf" shape="rect">[JSGF]</a>, which is
owned by Sun Microsystems, Inc., California, U.S.A.</p>
<h3 id="id-S1.1"><a id="S1.1" name="S1.1" shape="rect">1.1 Grammar
Processors and User Agents</a></h3>
<p>A <em>grammar processor</em> is any entity that accepts as input
grammars as described in this specification.</p>
<p>A <em>user agent</em> is a grammar processor that accepts user
input and matches that input against a grammar to produce a
recognition result that represents the detected input.</p>
<p>As the specification title implies, speech recognizers are an
important class of grammar processor. Another class of grammar
processor anticipated by this specification is a <a href=
"#term-dtmf" shape="rect">Dual-Tone Multi-Frequency</a> (DTMF)
detector. The type of input accepted by a user agent is determined
by the <a href="#S4.6" shape="rect"><code>mode</code></a> or modes
of grammars it can process: e.g. speech input for <a href="#S4.6"
shape="rect">"voice"</a> mode grammars and DTMF input for <a href=
"#AppE" shape="rect">"dtmf"</a> mode grammars.</p>
<p>For simplicity, throughout this document references to a speech
recognizer apply to other types of grammar processor unless
explicitly stated otherwise.</p>
<p>A <em>speech recognizer</em> is a user agent with the following
inputs and outputs:</p>
<ul>
<li>Input: A grammar or multiple grammars as defined by this
specification. These grammars inform the recognizer of the words
and patterns of words to listen for.</li>
<li>Input: An audio stream that may contain speech content that
matches the grammar(s).</li>
<li>Output: Descriptions of <em>results</em> that indicate details
about the speech content detected by the speech recognizer. The
format and details of the content of the result are outside the
scope of this specification. For informative purposes, most
practical recognizers will include at least a transcription of any
detected words.</li>
<li>Output: Error and other performance information may be provided
to the host environment: e.g. to a voice browser that incorporates
a grammar processor. The method of interaction with the host
environment is outside the scope of this document. The
specification does, however, require that a <a href="#S5" shape=
"rect">conformant grammar processor</a> inform the environment of
errors in parsing and other processing of grammar documents.</li>
</ul>
<h3 id="id-S1.2"><a id="S1.2" name="S1.2" shape="rect">1.2
Scope</a></h3>
<p>The primary use of a speech recognizer grammar is to permit a
speech application to indicate to a recognizer what it should
listen for, specifically:</p>
<ul>
<li>Words that may be spoken,</li>
<li>Patterns in which those words may occur,</li>
<li>Spoken language of each word.</li>
</ul>
<p>Speech recognizers may also support the Stochastic Language
Models (N-Gram) Specification <a href="#ref-ngram" shape=
"rect">[NGRAM]</a>. Both specifications define ways to set up a
speech recognizer to detect spoken input but define the word and
patterns of words by different and complementary means. Some
recognizers permit cross-references between grammars in the two
formats. The <a href="#S2.2" shape="rect">rule reference</a>
element of this specification describes how to reference an N-gram
document.</p>
<p>The grammar specification <em>does not address</em> a number of
other issues that affect speech recognition performance. Most of
the following capabilities are addressed by the context in which a
grammar is referenced or invoked: for example, through VoiceXML 2.0
<a href="#ref-vxml2" shape="rect">[VXML2]</a> or through a speech
recognizer API.</p>
<ul>
<li><em>Speaker adaptation data:</em> Some speech recognizers
support the ability to dynamically adjust to the voice of a speaker
and often the ability to store adaptation data for that voice for
future use. The speaker data may also include lists of words more
often spoken by the user. The grammar format does not explicitly
address these capabilities.</li>
<li><em>Speech recognizer configuration:</em> The grammar format
does not incorporate features for setting recognizer features such
as timeouts, recognition thresholds, search sizes or N-best result
counts.</li>
<li><em>Lexicon:</em> The grammar format does not address the
loading of lexicons or the pronunciation of words referenced by the
grammar. The W3C Voice Browser Working Group is considering the
development of a standard lexicon format. If and when a format is
developed appropriate updates will be made to this grammar
specification.</li>
<li><em>Other speech processing capabilities:</em> Speech
processing technology exists for language identification, speaker
verification (also known as voice printing), speaker recognition
(also known as speaker identification) amongst many other
capabilities. Although these technologies may be associated with a
speech recognizer they are outside the scope of this
specification.</li>
</ul>
<h3 id="id-S1.3"><a id="S1.3" name="S1.3" shape="rect">1.3 Grammar
Conversions</a></h3>
<p>The ABNF Form and XML Form <span>are</span> specified to ensure
that the two representations are semantically mappable. It should
be possible to automatically convert an ABNF Form grammar to an XML
Form grammar (or the reverse) so that the semantic performance of
the grammars are identical. Equivalence of semantic performance
implies that:</p>
<ol>
<li>Both grammars accept the same language as input and reject the
same language as input</li>
<li>Both grammars parse any input string identically</li>
</ol>
<p>The XSL Transformation document in <a href="#AppF" shape=
"rect">Appendix F</a> demonstrates automatic conversion from XML to
ABNF. The reverse conversion requires an ABNF parser and a
transformational program.</p>
<p>There are inherent limits to the automatic conversion to and
From ABNF Form and XML Form.</p>
<ul>
<li>Formatting <a href="#term-whitespace" shape="rect">white
space</a> cannot be preserved so a pretty-printable grammar in one
Form cannot guarantee automatic conversion to a pretty-printable
grammar in the other Form. Note: syntactically significant white
space is preserved.</li>
<li>Some XML constructs have no equivalent in ABNF: XML Schema, DTD,
character and entity declarations and references, processing
instructions, namespaces. The XML parser in a <a href="#S5.4"
shape="rect">conforming grammar processor</a> should expand all
character and entity references as defined in XML 1.0 <a href=
"#ref-xml" shape="rect">[XML]</a> prior to conversion to ABNF;
other constructs are lost. RDF <a href="#ref-rdf-syntax" shape=
"rect">[RDF-SYNTAX]</a> represents metadata as XML within XML Form
grammar but could not be effectively utilized in ABNF Form grammars
and so is not supported.</li>
<li>Comment ordering with respect to grammar constructs may be
modified.</li>
</ul>
<h3 id="id-S1.4"><a id="S1.4" name="S1.4" shape="rect">1.4 Semantic
Interpretation</a></h3>
<p>A speech recognizer is capable of matching audio input against a
grammar to produce a <em>raw text</em> transcription (also known as
<em>literal text</em>) of the detected input. A recognizer may be
capable of, but is not required to, perform subsequent processing
of the raw text to produce a <em>semantic interpretation</em> of
the input.</p>
<p>For example, the natural language utterance <em>"I want to book
a flight from Prague to Paris"</em> could result in the following
XML data structure. To perform this additional interpretation step
requires semantic processing instructions that may be contained
within a grammar that defines the legal spoken input or in an
associated document.</p>
<pre class="xml" xml:space="preserve">
  &lt;book-flight&gt;
    &lt;depart&gt;Prague&lt;/depart&gt;
    &lt;arrive&gt;Paris&lt;/arrive&gt;
  &lt;/book-flight&gt;
</pre>
<p>The Speech Recognition Grammar Specification provides syntactic
support for limited semantic interpretation. The <a href="#S2.6"
shape="rect"><code>tag</code></a> construct and the <a href="#S4.8"
shape="rect"><code>tag-format</code></a> <span>and <a href="#S4.12"
shape="rect"><code>tag</code></a></span> declarations provide a
placeholder for instructions to a semantic processor.</p>
<p>The <a href="http://www.w3.org/Voice/" shape="rect">W3C Voice
Browser Working Group</a> is presently developing the <em>Semantic
Interpretation for Speech Recognition</em> specification <a href=
"#ref-sem" shape="rect">[SEM]</a>. That specification defines a
language that can be embedded in tags within SRGS grammars to
perform the interpretation process. The semantic processing is
defined with respect to the <a href="#AppH" shape=
"rect"><em>logical parse structure</em></a> for grammar processing
(see <a href="#AppH" shape="rect">Appendix H</a>). Other tag
formats could be used but are outside the scope of the W3C
activities.</p>
<p>For examples of semantic interpretation in the latest working
draft see <a href="#ref-sem" shape="rect">[SEM]</a>.</p>
<p>The output of the semantic interpretation processor may be
represented using the <em>Natural Language Semantics Markup
Language</em> <a href="#ref-nlsml" shape="rect">[NLSML]</a>. This
XML representation of interpreted spoken input can be used to
transmit the result, as input to <em>VoiceXML 2.0</em> <a href=
"#ref-vxml2" shape="rect">[VXML2]</a> processing or in other
ways.</p>
<p>The semantic interpretation carried out in the speech
recognition process is typically characterized by:</p>
<ul>
<li><em>Restricted context:</em> the interpretation does not
resolve deictic or anaphoric references or other language forms
that span more than a single utterance. Example: if the utterance
<em>"I want to book a flight from Prague to Paris"</em> were
followed later by <em>"I want to continue from there to
London"</em> the reference to <em>"there"</em> could be resolved to
<em>"Paris"</em>. This requires analysis spanning more than one
utterance and is typically outside the scope of the speech
recognizer, but in scope for a dialog manager (e.g. a VoiceXML
application).</li>
<li><em>Domain-specific:</em> a speech recognition grammar is
typically restricted to a narrow domain of input (e.g. collect
flight booking data). Within this domain semantic interpretation is
an achievable task whereas semantic interpretation for an entire
language is an extraordinarily complex task.</li>
<li><em>Language-specific:</em> because each language has unique
linguistic structures the process of converting from a raw text to
a semantic result is necessarily language-specific.</li>
</ul>
<p>It is this restricted form of semantic interpretation that this
approach is intended to support. A VoiceXML application that
receives a speech result with semantic interpretation will
typically process the user input to carry out a dialog. The
application may also perform deeper semantic analysis, for example
resolving deictic or anaphoric references.</p>
<h3 id="id-S1.5"><a id="S1.5" name="S1.5" shape="rect">1.5 Embedded
Grammars</a></h3>
<p>The Speech Recognition Grammar Specification is designed to
permit ABNF Form and XML Form grammars to be embedded into other
documents. For example, VoiceXML 1.0 <a href="#ref-vxml1" shape=
"rect">[VXML1]</a> and VoiceXML 2.0 <a href="#ref-vxml2" shape=
"rect">[VXML2]</a> permit <a href=
"http://www.w3.org/TR/voicexml20/#dml3.1.1.1" shape="rect">inline
grammars</a> <a href="#ref-vxml2" shape="rect">[VXML2
&sect;3.1.1.1]</a> in which an ABNF Form grammar or XML Form
grammar is contained within a VoiceXML document.</p>
<p>Embedding an XML Form grammar within an XML document can be
achieved with XML namespaces <a href="#ref-xmlns" shape=
"rect">[XMLNS]</a> or by incorporating the grammar <a href="#AppC"
shape="rect">XML Schema definition</a> or <a href="#AppB" shape="rect">DTD</a>
into to enclosing document's schema or DTD.</p>
<p>An ABNF Form grammar may be embedded into any XML document as
character data. ABNF grammars will often contain angle brackets
which require special handling within XML. A <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-cdata-sect" shape=
"rect">CDATA</a> section <a href="#ref-xml" shape="rect">[XML
&sect;2.7]</a> or the escape sequences of "<code>&amp;lt;</code>"
and "<code>&amp;gt;</code>" may be required to create well-formed
XML. Note: angle brackets ('&lt;' and '&gt;') are used in ABNF to
delimit any <a href="#term-uri" shape="rect">URI</a>, <a href=
"#term-media-type" shape="rect">media type</a> or <a href="#S2.5"
shape="rect">repeat operator</a>.</p>
<h3 id="id-S1.6"><a id="S1.6" name="S1.6" shape="rect">1.6
Terminology</a></h3>
<dl>
<dt><b><em><a id="term-requirements" name="term-requirements"
shape="rect">Requirements terms</a></em></b></dt>
<dd>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in <a href=
"#ref-rfc2119" shape="rect">[RFC2119]</a>. However, for
readability, these words do not appear in all uppercase letters in
this specification.</dd>
<dt><br clear="none" />
<b><em><a id="term-uri" name="term-uri" shape="rect">URI: Uniform
Resource Identifier</a></em></b></dt>
<dd>A URI is a unifying syntax for the expression of names and
addresses of objects on the network as used in the World Wide Web.
A URI is defined as any legal '<code><a href=
"http://www.w3.org/TR/xmlschema-2/#anyURI" shape=
"rect">anyURI</a></code> ' primitive as defined in XML Schema Part
2: Datatypes <a href="#ref-schema2" shape="rect">[SCHEMA2
&sect;3.2.17]</a>. The XML Schema definition follows <a href=
"#ref-rfc2396" shape="rect">[RFC2396]</a> and <a href=
"#ref-rfc2732" shape="rect">[RFC2732]</a>. The syntax
representation of a URI differs between the ABNF Form and the XML
Form. Any relative URI reference must be resolved according to the
rules given in <a href="#S4.9.1" shape="rect">Section 4.9.1</a>.
<ul>
<li><b>ABNF URI</b>: in the ABNF Form of this specification a URI
is delimited by angle brackets ('&lt;' '&gt;'). For example,
<code>&lt;http://www.example.com/file-path&gt;</code></li>
<li><b>XML URI</b>: in the XML Form of this specification any URI
is provided as an attribute to an element; for example the <a href=
"#S2.2" shape="rect"><code>ruleref</code></a> and <a href="#S4.10"
shape="rect"><code>lexicon</code></a> elements.</li>
</ul>
</dd>
<dt><br clear="none" />
<b><em><a id="term-media-type" name="term-media-type" shape=
"rect">Media Type</a></em></b></dt>
<dd>A <em>media type</em> (defined in <a href="#ref-rfc2045" shape=
"rect">[RFC2045]</a> and <a href="#ref-rfc2046" shape=
"rect">[RFC2046]</a>) specifies the nature of a linked resource.
Media types are case insensitive. A list of registered media types
is available for download <a href="#ref-mimetypes" shape=
"rect">[TYPES]</a>. In places where a URI can be specified a media
type may be provided to indicate the content type of <a href=
"#term-uri" shape="rect">URI</a>.
<p>[See <a href="#AppG" shape="rect">Appendix G</a> for information
on media types for the ABNF and XML Forms of the Speech Recognition
Grammar Specification.]</p>
<ul>
<li><b>ABNF URI with Media Type</b>: in the ABNF Form a media type
may be attached as a postfix to any URI. The media type is
delimited by angle brackets ('&lt;' '&gt;') and the URI and media
type are separated by a tilde character ('~') without intervening
<a href="#term-whitespace" shape="rect">white space</a>. For
example,<br clear="none" />
<code>&lt;http://example.com/file-path&gt;~&lt;media-type&gt;</code></li>
<li><b>XML URI with Media Type</b>: in the XML Form any element
that carries a URI attribute may carry a <code>type</code>
attribute.</li>
</ul>
</dd>
<dt><br clear="none" />
<b><em><a id="term-language" name="term-language" shape=
"rect">Language identifier</a></em></b></dt>
<dd>A <em>language identifier</em> labels information content as
being of a particular human language variant. Following the
<a href="http://www.w3.org/TR/2000/REC-xml-20001006#sec-lang-tag"
shape="rect">XML specification for language identification</a>
<a href="#ref-xml" shape="rect">[XML &sect;2.12]</a> a legal
language identifier in ABNF Form grammars and XML Form grammars is
identified by an RFC 3066 <a href="#ref-rfc3066" shape=
"rect">[RFC3066]</a> code. A language code is required by RFC 3066.
A country code or other subtag identifier is optional by RFC 3066.
A grammar's <a href="#S4.5" shape="rect">language declaration</a>
declares the language of a grammar. Additionally a legal rule
expansion may be labeled by its <a href="#S2.7" shape=
"rect">language content</a>.</dd>
<dt><br clear="none" />
<b><em><a id="term-whitespace" name="term-whitespace" shape=
"rect">White space</a></em></b></dt>
<dd>White space consists of one or more space (#x20) characters,
carriage returns, line feeds, or tabs. The normative definition for
both ABNF and XML follows the <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-common-syn" shape=
"rect">XML <em>white space</em> definition</a> <a href="#ref-xml"
shape="rect">[XML &sect;2.3]</a>. ABNF processors must also follow
the <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-line-ends" shape=
"rect">end-of-line handling</a> of XML 1.0 <a href="#ref-xml"
shape="rect">[XML &sect;2.11]</a>.</dd>
<dt><br clear="none" />
<b><em><a id="term-dtmf" name="term-dtmf" shape=
"rect">DTMF</a></em></b></dt>
<dd>DTMF (Dual Tone Multiple Frequency) is an <a href=
"http://www.itu.int/" shape="rect">ITU</a> standard for telephony
signaling. ITU Recommendation Q.23 defines DTMF generation. ITU
Recommendation Q.24 <a href="#ref-q24" shape="rect">[Q24]</a>
defines DTMF reception. A grammar processor that accepts DTMF input
should implement Q.24.</dd>
</dl>
<h2 id="id-S2"><a id="S2" name="S2" shape="rect">2. Rule
Expansions</a></h2>
<ul>
<li class="tocline">2.1 <a href="#S2.1" shape=
"rect">Tokens</a></li>
<li class="tocline">2.2 <a href="#S2.2" shape="rect">Rule
References</a>
<ul>
<li class="tocline">2.2.1 <a href="#S2.2.1" shape="rect">Local
References</a></li>
<li class="tocline">2.2.2 <a href="#S2.2.2" shape="rect">External
Reference by URI</a></li>
<li class="tocline">2.2.3 <a href="#S2.2.3" shape="rect">Special
Rules</a></li>
<li class="tocline">2.2.4 <a href="#S2.2.4" shape=
"rect">Referencing N-gram Documents</a></li>
</ul>
</li>
<li class="tocline">2.3 <a href="#S2.3" shape="rect">Sequences and
Encapsulation</a></li>
<li class="tocline">2.4 <a href="#S2.4" shape=
"rect">Alternatives</a>
<ul>
<li class="tocline">2.4.1 <a href="#S2.4.1" shape=
"rect">Weights</a></li>
</ul>
</li>
<li class="tocline">2.5 <a href="#S2.5" shape="rect">Repeats</a>
<ul>
<li class="tocline">2.5.1 <a href="#S2.5.1" shape="rect">Repeat
Probabilities</a></li>
</ul>
</li>
<li class="tocline">2.6 <a href="#S2.6" shape="rect">Tags</a></li>
<li class="tocline">2.7 <a href="#S2.7" shape=
"rect">Language</a></li>
<li class="tocline">2.8 <a href="#S2.8" shape=
"rect">Precedence</a></li>
</ul>
<p>A <em>legal rule expansion</em> is any legal <a href="#S2.1"
shape="rect">token</a>, <a href="#S2.2" shape="rect">rule
reference</a>, <a href="#S2.6" shape="rect">tag</a>, or any logical
combination of legal rule expansions as <a href="#S2.3" shape=
"rect">sequence</a>, <a href="#S2.4" shape="rect">alternatives</a>,
<a href="#S2.5" shape="rect">repeated expansion</a> or <a href=
"#S2.7" shape="rect">language-attributed expansion</a>.</p>
<p>A rule expansion is formally a <em>regular expression</em> (see,
for example, <a href="#ref-hu79" shape="rect">[HU79]</a>).</p>
<p>A <a href="#S3" shape="rect"><em>rule definition</em></a>
associates a legal rule expansion with a rulename.</p>
<h3 id="id-S2.1"><a id="S2.1" name="S2.1" shape="rect">2.1
Tokens</a></h3>
<p>A <em>token</em> (a.k.a. a terminal symbol) is the part of a
grammar that defines words or other entities that may be spoken.
Any legal token is a <a href="#S2" shape="rect">legal
expansion</a>.</p>
<p>For speech recognition, a token is typically an orthographic
entity of the <a href="#S2.7" shape="rect">language</a> being
recognized. However, a token may be any string that the speech
recognizer can convert to a phonetic representation.</p>
<p><a id="token-content" name="token-content" shape="rect"></a>
<em>Token Content:</em> In both the <a href="#S2.1-xml" shape=
"rect">XML Form</a> and <a href="#S2.1-abnf" shape="rect">ABNF
Form</a> any unmarked text within a rule definition, except
<a href="#S3.3" shape="rect">example phrases</a> (XML only) or
<a href="#S2.6" shape="rect">tag content</a>, is <em>token
content</em>. The unmarked text is delimited by any syntactic
construct of the grammar form (see below for details on the ABNF
Form and XML Form). For each token content span in a grammar the
grammar processor applies the following <a href="#tokenization"
shape="rect">tokenization</a>, <a href="#ws-normalization" shape=
"rect">white space normalization</a>, <a href=
"#token-normalization" shape="rect">token normalization</a> and
<a href="#pron-lookup" shape="rect">pronunciation lookup</a>
processes. All token content in both the XML Form and ABNF Form is
treated as <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#charsets" shape=
"rect">Characters</a> in <a href="#ref-xml" shape="rect">[XML]</a>.
(informative: XML specifies Characters by reference to ISO/IEC
10646 <a href="#ref-iso10646" shape="rect">[ISO/IEC 10646]</a> and
Unicode <a href="#ref-unicode" shape="rect">[Unicode]</a>.)</p>
<a id="tokenization" name="tokenization" shape="rect"></a>
<p><em>Tokenization behavior</em>: Text spans containing token
sequences are delimited as follows:</p>
<ul>
<li>XML Form only: a &lt;token&gt; element may contain character
data only. The character data is treated as a single unnormalized
token. The character data must not contain any double quote
characters.</li>
<li>Any token in ABNF Form or XML Form (except within &lt;token&gt;
element in XML Form) may be delimited by double quotes. The text
contained within the double quotes is an unnormalized token. The
text must not contain any double quote characters. A token
delimited by double quotes may contain white space.</li>
<li>Any token content not delimited by a &lt;token&gt; element or
double quotes is treated as a sequence of white-space-delimited
tokens. Each token contained in the token content is delimited at
the start and at the end by any white space character or any
syntactic construct that delimits a token content span. The
syntactic constructs that delimit token content are different for
the ABNF Form and XML Form. These tokens cannot contain white space
characters.</li>
</ul>
<table border="1" cellpadding="3" summary="Token Syntax Examples">
<tr>
<td colspan="1" rowspan="1"><b>Token type</b></td>
<td colspan="1" rowspan="1"><b>Form</b></td>
<td colspan="1" rowspan="1"><b>Example</b></td>
</tr>
<tr>
<td colspan="1" rowspan="1">Single unquoted token</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">hello</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Single unquoted token:
non-alphabetic</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">2</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Single quoted token: including white
space</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">"San Francisco"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Single quoted token: no white
space</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">"hello"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Two tokens delimited by white
space</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">bon voyage</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Four tokens delimited by white
space</td>
<td colspan="1" rowspan="1">ABNF &amp; XML</td>
<td colspan="1" rowspan="1">this is a test</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Single XML token in &lt;token&gt;</td>
<td colspan="1" rowspan="1">XML Only</td>
<td colspan="1" rowspan="1">&lt;token&gt;San
Francisco&lt;/token&gt;</td>
</tr>
</table>
<a id="ws-normalization" name="ws-normalization" shape="rect"></a>
<p><em>White Space Normalization:</em> White space must be
normalized when contained in any token delimited by a &lt;token&gt;
elements or by double quotes. Leading and trailing white space
characters are stripped. Any token-internal white space character
or sequence is collapsed to a single space character (#x20). For
example, the following are all normalized to the same string, "San
Francisco".</p>
<pre class="abnf" xml:space="preserve">
  "San Francisco"
  " San Francisco "
  "San 
  Francisco"
  " San   Francisco "
</pre>
<p>Because the presence of white space within a token is
significant the following are distinct tokens.</p>
<pre class="abnf" xml:space="preserve">
  "San Francisco"
  "SanFrancisco"
  "San_Francisco"
</pre>
<a id="token-normalization" name="token-normalization" shape=
"rect"></a>
<p><em>Token Normalization:</em> Other normalization processes are
applied to the white space normalized token according to the
language and the capabilities of the speech recognizer.</p>
<p>Grammar processors may assume <a href=
"http://www.w3.org/TR/2003/WD-charmod-20030822/#sec-Normalization" shape=
"rect">Early Uniform Normalization</a> as defined in the Character
Model for the World Wide Web 1.0 <a href="#ref-charmod" shape=
"rect">[CHARMOD &sect;4]</a>.</p>
<a id="pron-lookup" name="pron-lookup" shape="rect"></a>
<p><em>Pronunciation Lookup:</em> To match spoken (audio) input to
a grammar a speech recognition must be capable of modelling the
audio patterns of any token in a grammar. Speech recognizers employ
a diverse set of techniques for performing this key recognition
process. The following is an informative description of techniques
that a speech recognizer may apply based on conventional large
vocabulary speech recognition technology.</p>
<p>A large vocabulary speech recognizer converts each normalized
token to a phoneme sequence or a set of possible phoneme sequences.
Conversion of an orthographic form (token) to the spoken form
(phonemes) is a highly language-specific process. In many cases the
conversion is even specific to a national variant, regional dialect
or other variant of the language. For example, for some tokens
Parisian French, Quebec French and Swiss French will each convert
to different pronunciations.</p>
<p>The text-to-phoneme conversion in a large vocabulary speech
recognizer may involve some or all of the following
sub-processes.</p>
<ul>
<li><em>Pronunciation lexicon lookup:</em> One of possibly many
lexicons available to a recognizer can provide the phoneme sequence
for a token. Both the ABNF Form and XML Form permit a grammar to
specify one or more <a href="#S4.10" shape="rect">lexicon</a>
documents. Recognizers typically provide a built-in lexicon for
each supported language though the coverage will vary between
recognizers. The algorithm by which the lookup resolves a token to
a pronunciation is defined by the lexicon format and/or the speech
recognizer and may be language-specific. Case-insensitive string
matching is recommended.</li>
<li><em>Morphological analysis:</em> a recognizer may be capable of
determining the transformation from a base token and phoneme string
to a morphological variant and its pronunciation. For example given
the pronunciation for "Hyundai" a rule could infer the
pronunciation for the pluralized form "Hyundai's".</li>
<li><em>Automatic text-to-phoneme conversion:</em> for many, but
not all, languages and scripts there are rules that automatically
convert a token into a phoneme sequence. For example, in English
most but not all words ending with the letter sequence "ise" end
with the phoneme sequence "ai z". A speech recognizer may use
automated conversion to infer pronunciations for tokens that cannot
be looked up in a lexicon.</li>
</ul>
<p>Any language is likely to have other specialized processes for
determining a pronunciation for a token. For example, for Japanese
special techniques are required for Kanji and each Kana form.</p>
<p>For any language and recognizer there may be variation in
coverage and completeness of the language's tokens.</p>
<p>When a grammar processor handles a grammar containing a token
that it cannot convert to phonemic form or otherwise use in the
speech recognition processing of audio it should inform the hosting
environment.</p>
<a id="token-limitations" name="token-limitations" shape=
"rect"></a>
<p><em>Limitations of token handling:</em> the following is
informative guidance to grammar developers.</p>
<p>The Pronunciation Lexicon activity <a href="#ref-lex" shape=
"rect">[LEX]</a> of the W3C Voice Browser Working Group will
provide guidance on the token-handling processes outlined
above.</p>
<p>Token handling will vary between recognizers and will vary
between languages.</p>
<p>Grammar authors can improve document portability by avoiding
characters and forms in tokens that do not have obvious
pronunciations in the language. For English, the following are ways
to handle some orthographic forms:</p>
<ul>
<li>Acronyms should be avoided. Alphabetic characters should be
widely available. For example, replace "USA" by "u s a"; replace
"W3C" by "w three c"; replace "IEEE" by "i triple e".</li>
<li>Abbreviations should be replaced by the unabbreviated form. For
example, replace "Dr." by "drive" or "doctor".</li>
<li>Most punctuation should be expanded to a spelled form. For
example replace "&amp;" by "ampersand" or "and"; replace "+" by
"plus"; replace "&lt;" by "less than" or "open angle bracket".</li>
<li>A grammar processor should support digits (e.g. "0" though "9"
for European scripts). Other natural numbers should be replaced by
spelled forms. For example, for US English replace "10" by "ten"
and "1000" by "thousand".</li>
<li>Grammar authors should consider the possibility that a grammar
will be used to interpret input in a non-speech recognition device.
For example, grammars can be used to process text strings from
keyboard input, text telephone services, pen input and other text
modalities. To facilitate text input a grammar should contain
standard orthographic tokens of the language. That is, to
facilitate non-speech recognition input the grammar should contain
standard spellings of natural language words to the greatest extent
possible.</li>
</ul>

<h4 id="id-S2.1-abnf"><a id="S2.1-abnf" name="S2.1-abnf" shape=
"rect">ABNF Form</a></h4>
<p>Any plain text within a rule definition is <a href=
"#token-content" shape="rect">token content</a>. The <a href=
"#AppD" shape="rect">ABNF Syntax (Appendix D)</a> normatively
defines the token parsing behavior.</p>
<p>A <a href="#S2.7-abnf" shape="rect">language attachment</a> may
be provided for any token. When attached to a token the language
modifies the handling of that token only.</p>
<p><em>Informative</em></p>
<p>The rule expansion of a <a href="#S3.1" shape="rect">rule
definition</a> is delimited at the start and end by equals sign
('=') and semicolon (';') respectively. Any leading plain text of
the rule expansion is delimited by ('=') and similarly any final
plain text is closed by semicolon.</p>
<p>Within a rule expansion the following symbols have syntactic
function and delimit plain text.</p>
<ul>
<li>Dollar sign ('$') and angle brackets ('&lt;' and '&gt;') when
needed mark <a href="#S2.2" shape="rect">rule references</a></li>
<li>Parentheses ('(' and ')') may enclose any <a href="#S2.3"
shape="rect">rule expansion</a></li>
<li>Vertical bar ('|') delimits <a href="#S2.4" shape=
"rect">alternatives</a></li>
<li>Forward slashes ('/' and '/') delimit any <a href="#S2.4.1"
shape="rect">weights</a> on alternatives</li>
<li>Angle brackets ('&lt;' and '&gt;') delimit any <a href="#S2.5"
shape="rect">repeat operator</a></li>
<li>Square brackets ('[' and ']') delimit any <a href="#S2.5"
shape="rect">optional expansion</a></li>
<li>Curly brackets ('{' and '}') delimit any <a href="#S2.6" shape=
"rect">tag</a></li>
<li>Exclamation point ('!') prefixes any <a href="#S2.7" shape=
"rect">language identifier</a></li>
</ul>
<p>Within plain text regions delimited by these characters the
<a href="#tokenization" shape="rect">tokenization</a>, <a href=
"#ws-normalization" shape="rect">white space normalization</a>,
<a href="#token-normalization" shape="rect">token normalization</a>
and <a href="#pron-lookup" shape="rect">pronunciation lookup</a>
processes described above apply.</p>
<h4 id="id-S2.1-xml"><a id="S2.1-xml" name="S2.1-xml" shape=
"rect">XML Form</a></h4>
<p>Any <code>token</code> element explicitly delimits a <a href=
"#S2.1" shape="rect">single token</a> as described above. The
<code>token</code> element may include an optional <a href=
"#S2.7-xml" shape="rect"><code>xml:lang</code></a> attribute to
indicate the <a href="#S2.7" shape="rect">language</a> of the
contained token.</p>
<p>Any other character data within a <a href="#S3.1" shape=
"rect">rule</a> element (rule definition) or <a href="#S2.3" shape=
"rect">item</a> element is <a href="#token-content" shape=
"rect">token content</a>. Note that character data within <a href=
"#S2.6" shape="rect">tag</a> or <a href="#S3.3" shape=
"rect">example</a> is not token text.</p>

<h3 id="id-S2.2"><a id="S2.2" name="S2.2" shape="rect">2.2 Rule
Reference</a></h3>
<p>Any legal rule reference is a <a href="#S2" shape=
"rect"><em>legal rule expansion</em></a> .</p>
<p><em>Rulenames</em>: Every <a href="#S3.1" shape="rect">rule
definition</a> has a local name that must be unique within the
scope of the grammar in which it is defined. A rulename must match
the <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-common-syn" shape=
"rect">"Name" Production</a> of XML 1.0 <a href="#ref-xml" shape=
"rect">[XML &sect;2.3]</a> and be a legal XML ID. <a href="#S3.1"
shape="rect">Section 3.1</a> documents the rule definition
mechanism and the legal naming of rules.</p>
<p>This table summarizes the various forms of rule reference that
are possible within and across grammar documents.</p>
<p>Note: an XML Form grammar document must provide one and only one
of the <code>uri</code> or <code>special</code> attributes on a
<code>ruleref</code> element. There is no equivalent constraint in
ABNF since the syntactic forms are distinct.</p>
<table cellpadding="3" border="1" summary="Rule Reference Syntax">
<tbody>
<tr>
<td rowspan="1" colspan="1"><b>Reference type</b></td>
<td rowspan="1" colspan="1"><b>ABNF Form</b></td>
<td rowspan="1" colspan="1"><b>XML Form</b></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.1">2.2.1</a>:
<span>Explicit</span> local rule reference</td>
<td rowspan="1" colspan="1"><code>$rulename</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref
uri="#rulename"/&gt;</code></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.2">2.2.2</a>:
<span>Explicit</span> reference to a named rule of a
grammar identified by a <a href="#term-uri">URI</a></td>
<td rowspan="1" colspan="1">
<code>$&lt;grammarURI#rulename&gt;</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref
uri="grammarURI#rulename"/&gt;</code></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.2"
shape="rect">2.2.2</a>: <span>Implicit</span> reference to the
root rule of a grammar identified by a
<a href="#term-uri">URI</a></td>
<td rowspan="1" colspan="1"><code>$&lt;grammarURI&gt;</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref
uri="grammarURI"/&gt;</code></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.2">2.2.2</a>:
<span>Explicit</span> reference to a named rule of a grammar
identified by a <a href="#term-uri">URI</a> with a <a href=
"#term-media-type">media type</a></td>
<td rowspan="1" colspan="1">
<code>$&lt;grammarURI#rulename&gt;~&lt;media-type&gt;</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref
uri="grammarURI#rulename" type="media-type"/&gt;</code></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.2">2.2.2</a>:
<span>Implicit</span> reference to the root rule of a grammar
identified by a <a href="#term-uri">URI</a> with a <a href=
"#term-media-type">media type</a></td>
<td rowspan="1" colspan="1">
<code>$&lt;grammarURI&gt;~&lt;media-type&gt;</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref uri="grammarURI"
type="media-type"/&gt;</code></td>
</tr>
<tr>
<td rowspan="1" colspan="1"><a href="#S2.2.3">2.2.3</a>:
Special rule definitions</td>
<td rowspan="1" colspan="1"><code>$NULL<br clear="none" />
$VOID<br clear="none" />
$GARBAGE</code></td>
<td rowspan="1" colspan="1"><code>&lt;ruleref
special="NULL"/&gt;<br clear="none" />
&lt;ruleref special="VOID"/&gt;<br clear="none" />
&lt;ruleref special="GARBAGE"/&gt;</code></td>
</tr>
</tbody>
</table>
<h4 id="id-S2.1.1"><a id="S2.2.1" name="S2.2.1" shape="rect">2.2.1
Local References</a></h4>
<p>When referencing rules defined locally (defined in the same
grammar as contains the reference), always use a simple rulename
reference which consists of the local rulename only. The ABNF Form
and XML Form have a different syntax for representing a simple
rulename reference.</p>
<blockquote>
<h4 id="id-S2.1.1-abnf">ABNF Form</h4>
<p>The simple rulename reference is prefixed by a "$"
character.</p>
<pre class="abnf" xml:space="preserve">
$city
$digit
</pre>
<h4 id="id-S2.1.1-xml">XML Form</h4>
<p>The <code>ruleref</code> element is an empty element with a
<code>uri</code> attribute that specifies the rule reference as a
<em>same-document reference <a href="#term-uri" shape=
"rect">URI</a></em> <a href="#ref-rfc2396" shape=
"rect">[RFC2396]</a>: that is, the attribute consists only of the
number sign ('#') and the fragment identifier that indicates the
locally referenced rulename.</p>
<pre class="xml" xml:space="preserve">
&lt;ruleref uri="#city"/&gt;
&lt;ruleref uri="#digit"/&gt;
</pre></blockquote>
<h4 id="id-S2.2.2"><a id="S2.2.2" name="S2.2.2" shape="rect">2.2.2
External Reference by URI</a></h4>
<p>References to rules defined in other grammars are legal under
the conditions defined in <a href="#S3" shape="rect">Section 3</a>.
The external reference must identify the external grammar by
<a href="#term-uri" shape="rect">URI</a> and may identify a
specific rule within that grammar. If the fragment identifier that
would indicate a rulename is omitted, then the reference
<span>implicitly</span> targets the <a href="#S4.7" shape=
"rect"><code>root</code></a> rule of the external grammar.</p>
<p>Any externally-referenced rule may be <em>activated</em> for
recognition. That is it may define the top-level syntax of spoken
input. For instance, VoiceXML <a href="#ref-vxml2" shape=
"rect">[VXML2]</a> grammar activation may explicitly reference one
or more public rules (see <a href="#S3.2" shape="rect">Section
3.2</a>) and/or implicitly reference the root rule (see <a href=
"#S4.7" shape="rect">Section 4.7</a>).</p>
<p>A URI reference is illegal if the referring document and
referenced document have different modes. For instance, it is
illegal to reference a "dtmf" grammar from a "voice" grammar. (See
<a href="#S4.6" shape="rect">Section 4.6</a> for additional detail
on modes).</p>
<p><span>A resource indicated by an <a href="#term-uri" shape=
"rect">URI</a> reference may be available in one or more <a href=
"#term-media-type" shape="rect">media types</a>. The grammar author
may specify the preferred media-type via the <code>type</code>
attribute (XML form) or in angle braces following the URI (ABNF
form).</span>When the content represented by a URI is available in
many data formats, a grammar processor may use the <span>preferred
media-</span>type to influence which of the multiple formats is
used. For instance, on a server implementing HTTP content
negotiation, the processor may use the <span>preferred
media-</span>type to order the preferences in the negotiation.</p>
<p>The resource representation delivered by dereferencing the URI
reference may be considered in terms of two types. The
<i>declared media-type</i> is the asserted value for the resource
and the <i>actual media-type</i> is the true format of its content.
The actual media-type should be the same as the declared
media-type, but this is not always the case (e.g. a misconfigured
HTTP server might return <code>text/plain</code> for an
<code>application/srgs+xml</code> document). A specific URI scheme
may require that the resource owner always, sometimes, or never
return a media-type. The declared media-type is the value returned
by the resource owner or, if none is returned, the preferred media
type given in the grammar. There may be no declared media-type if
the resource owner does not return a value and no preferred type is
specified. Whenever specified, the declared media-type is
authoritative.</p>
<p>Three special cases may arise. The declared media-type may not
be supported by the processor; this is an error. The declared
media-type may be supported but the actual media-type may not
match; this is also an error. Finally, there may be no declared
media-type; the behavior depends on the specific URI scheme and the
capabilities of the grammar processor. For instance, HTTP 1.1
allows document introspection (see <a href="#ref-rfc2616" shape=
"rect">RFC 2616</a>, section 7.2.1), the data scheme falls back to
a default media type, and local file access defines no guidelines.
The following table provides some informative examples:</p>
<table width="100%" border="1" cellpadding="3" summary=
"Media type examples">
<tr>
<td width="20%" rowspan="1" colspan="1"></td>
<td colspan="2" rowspan="1">
<div align="center"><b>HTTP 1.1 request</b></div>
</td>
<td colspan="2" rowspan="1">
<div align="center"><b>Local file access</b></div>
</td>
</tr>
<tr>
<td width="20%" rowspan="1" colspan="1">Media-type returned by the
resource owner</td>
<td width="20%" rowspan="1" colspan="1">text/plain</td>
<td width="20%" rowspan="1" colspan="1">application/srgs+xml</td>
<td width="20%" rowspan="1" colspan="1">&lt;none&gt;</td>
<td rowspan="1" colspan="1">&lt;none&gt;</td>
</tr>
<tr>
<td width="20%" rowspan="1" colspan="1">Preferred media-type
appearing in the grammar</td>
<td colspan="2" rowspan="1">Not applicable; the returned type takes
precedence</td>
<td width="20%" rowspan="1" colspan="1">application/srgs+xml</td>
<td rowspan="1" colspan="1">&lt;none&gt;</td>
</tr>
<tr>
<td width="20%" rowspan="1" colspan="1">Declared media-type</td>
<td width="20%" rowspan="1" colspan="1">text/plain</td>
<td width="20%" rowspan="1" colspan="1">application/srgs+xml</td>
<td width="20%" rowspan="1" colspan="1">application/srgs+xml</td>
<td rowspan="1" colspan="1">&lt;none&gt;</td>
</tr>
<tr>
<td width="20%" rowspan="1" colspan="1">Behavior if the actual
media-type is application/srgs+xml</td>
<td width="20%" rowspan="1" colspan="1">Error; the declared and
actual types do not match</td>
<td colspan="2" rowspan="1">The declared and actual types match;
success if application/srgs+xml is supported by the grammar
processor; otherwise an error</td>
<td rowspan="1" colspan="1">Scheme specific; the grammar processor
might introspect the document to determine the type.</td>
</tr>
</table>
<p>See <a href="#AppG" shape="rect">Appendix G</a> for a summary of
the status for media types for ABNF Form and XML Form grammars.</p>
<blockquote>
<h4 id="id-S2.2.2-abnf">ABNF Form</h4>
<p>In ABNF an external reference by URI is represented by a dollar
sign ('$') followed immediately by either an <a href="#term-uri"
shape="rect">ABNF URI</a> or <a href="#term-media-type" shape=
"rect">ABNF URI with media type</a>. There must be no <a href=
"#term-whitespace" shape="rect">white space</a> between the dollar
sign and the URI.</p>
<pre class="abnf" xml:space="preserve">
// References to specific rules of an external grammar
$&lt;http://grammar.example.com/world-cities.gram#canada&gt;
$&lt;http://grammar.example.com/numbers.gram#digit&gt;

// <span>Implicit</span> reference to the root rule of an external grammar
$&lt;../date.gram&gt;

// References with associated media types
$&lt;http://grammar.example.com/world-cities.gram#canada&gt;~&lt;application/srgs&gt;
$&lt;../date.gram&gt;~&lt;application/srgs&gt;
</pre>
<p>Note: the media type of <code>"application/srgs"</code> has been
requested for ABNF Form grammars. See <a href="#AppG" shape=
"rect">Appendix G</a> for details.</p>
<h4 id="id-S2.2.2-xml">XML Form</h4>
<p>An XML rule reference is represented by a <code>ruleref</code>
element with a <code>uri</code> attribute that defines the <a href=
"#term-uri" shape="rect">URI</a> of the referenced grammar and rule
within it. If a fragment identifier is appended then the identifier
indicates a specific rulename being referenced. If the fragment
identifier is omitted then the reference is
<span>(implicitly)</span> to the root rule of the referenced
grammar.</p>
<p>The optional <code>type</code> attribute specifies the <a href=
"#term-media-type" shape="rect">media type</a> of the grammar
containing the reference.</p>
<pre class="xml" xml:space="preserve">
&lt;!-- References to specific rules of an external grammar --&gt;
&lt;ruleref uri="http://grammar.example.com/world-cities.<span>grxml</span>#canada"/&gt;
&lt;ruleref uri="http://grammar.example.com/numbers.<span>grxml</span>#digit"/&gt;

&lt;!-- <span>Implicit</span> reference to the root rule of an external grammar --&gt;
&lt;ruleref uri="../date.<span>grxml</span>"/&gt;

&lt;!-- References with associated media types --&gt;
&lt;ruleref uri="http://grammar.example.com/world-cities.<span>grxml</span>#canada"
         type="application/srgs+xml"/&gt;
&lt;ruleref uri="../date.<span>grxml</span>" type="application/srgs+xml"/&gt;
</pre>
<p>Note: the media type <code>"application/srgs+xml"</code> has
been requested for XML Form grammars. See <a href="#AppG" shape=
"rect">Appendix G</a> for details on media types for grammars.</p>
</blockquote>
<h4 id="id-S2.2.3"><a id="S2.2.3" name="S2.2.3" shape="rect">2.2.3
Special Rules</a></h4>
<p>Several rulenames are defined to have specific interpretation
and processing by a speech recognizer. A grammar must not redefine
these rulenames.</p>
<p>In the ABNF Form a special rule reference is syntactically
identical to a <a href="#S2.2.1" shape="rect">local rule
reference</a>. However, the names of the special rules are
<em>reserved</em> to prevent a <a href="#S3.1" shape="rect">rule
definition</a> with the same name.</p>
<p>In the XML Form a special rulename is represented with the
<code>special</code> attribute on a <code>ruleref</code> element.
It is illegal to provide both the <code>special</code> and the
<code>uri</code> attributes.</p>
<dl>
<dt><b>NULL</b></dt>
<dd>Defines a rule that is automatically matched: that is, matched
without the user speaking any word.
<p>ABNF Form: <code>$NULL</code><br clear="none" />
XML Form: <code>&lt;ruleref special="NULL"/&gt;</code></p>
</dd>
<dt><b>VOID</b></dt>
<dd>Defines a rule that can never be spoken. Inserting VOID into a
sequence automatically makes that sequence unspeakable.
<p>ABNF Form: <code>$VOID</code><br clear="none" />
XML Form: <code>&lt;ruleref special="VOID"/&gt;</code></p>
</dd>
<dt><b>GARBAGE</b></dt>
<dd>Defines a rule that may match any speech up until the next rule
match, the next token or until the end of spoken input. A grammar
processor must accept grammars that contain special references to
GARBAGE. The behavior GARBAGE rule is implementation-specific. A
user agent should be capable of matching arbitrary spoken input up
to the next token but may treat GARBAGE as equivalent to NULL
(match no spoken input).
<p>ABNF Form: <code>$GARBAGE</code><br clear="none" />
XML Form: <code>&lt;ruleref special="GARBAGE"/&gt;</code></p>
<b>Informative example:</b> given suitable definitions of US cities
and states, a speech recognizer may implement the following ABNF
and XML rule definitions to match <em>"Philadelphia in the great
state of Pennsylvania"</em> as well as simply <em>"Philadelphia
Pennsylvania"</em>.
<pre class="abnf" xml:space="preserve">
$location = $city $GARBAGE $state;
</pre>
<pre class="xml" xml:space="preserve">
&lt;rule id="location"&gt;
  &lt;ruleref uri="#city"/&gt;
  &lt;ruleref special="GARBAGE"/&gt;
  &lt;ruleref uri="#state"/&gt;
&lt;/rule&gt;
</pre></dd>
</dl>
<h4 id="id-S2.2.4"><a id="S2.2.4" name="S2.2.4" shape="rect">2.2.4
Referencing N-gram Documents (Informative)</a></h4>
<p>The W3C Voice Browser Working Group has released a Working Draft
for the Stochastic Language Models (N-Gram) Specification <a href=
"#ref-ngram" shape="rect">[NGRAM]</a>. These two specifications
represent different and complementary ways of informing a speech
recognizer of which words and patterns of words to listen for.</p>
<p>A speech recognizer may choose to support the Speech Recognition
N-Gram Grammar Specification in addition to the speech recognition
grammar defined in this document.</p>
<p>If a speech recognizer supports both grammar representations it
may optionally support references between the two formats. Grammars
defined in the ABNF Form or XML Form may reference start symbols of
N-Gram documents and vice versa.</p>
<p>The syntax for referencing an N-Gram is the same as referencing
externally defined ABNF Form or XML Form grammar documents. A media
type is recommended on a reference to an N-gram document. The
Working Group has not yet applied for a type on N-gram documents so
no example is given. The fragment identifier (a rulename when
referencing ABNF Form and XML Form grammars) identifies a <em>start
symbol</em> as defined by the N-Gram specification. If the start
symbol is absent the N-Gram, as a whole, is referenced as defined
in the N-Gram specification.</p>
<blockquote>
<h4 id="id-S2.2.4-abnf">ABNF Form</h4>
<p><a href="#S2.2.2" shape="rect">URI references</a> to N-Gram
documents follow the same syntax as references to other ABNF or XML
Form grammar documents. The following are examples of references to
an N-Gram document via an <a href="#S2.2.2" shape="rect">explicit
rule reference</a> and a<span>n implicit</span> reference to the
<a href="#S2.2.2" shape="rect">root rule</a>.</p>
<pre class="abnf" xml:space="preserve">
$&lt;http://grammar.example.com/ngram.xml#StartSymbol&gt;
$&lt;http://grammar.example.com/ngram.xml&gt;
</pre>
<h4 id="id-S2.2.4-xml">XML Form</h4>
<p><a href="#S2.2.2" shape="rect">URI references</a> to N-Gram
documents follow the same syntax as reference to other ABNF Form
and XML Form grammar documents. The following are examples of
references to an N-Gram document via an <a href="#S2.2.2" shape=
"rect">explicit rule reference</a> and a<span>n implicit</span>
reference to the <a href="#S2.2.2" shape="rect">root rule</a>.</p>
<pre class="xml" xml:space="preserve">
&lt;ruleref uri="http://grammar.example.com/ngram.xml#StartSymbol"/&gt;
&lt;ruleref uri="http://grammar.example.com/ngram.xml"/&gt;
</pre></blockquote>
<h3 id="id-S2.3"><a id="S2.3" name="S2.3" shape="rect">2.3
Sequences and Encapsulation</a></h3>
<p>A <em>sequence</em> of legal rule expansions is itself a
<a href="#S2" shape="rect">legal rule expansion</a>.</p>
<p>The sequence of rule expansions implies the temporal order in
which the expansions must be detected by the <a href="#S1.1" shape=
"rect">user agent</a>. This constraint applies to sequences of
tokens, sequences of rule references, sequences of tags,
parentheticals and all combinations of these rule expansions.</p>
<p>Both the ABNF Form and XML Form provide syntax for encapsulating
any expansion. This is used, for example, to attach a <a href=
"#S2.5" shape="rect">repeat operator</a>, a <a href="#S2.7" shape=
"rect">language identifier</a> or to ensure correct <a href="#S2.8"
shape="rect">precedence</a> in parsing (ABNF only).</p>
<blockquote>
<h4 id="id-S2.3-abnf">ABNF Form</h4>
<p>A sequence of legal expansions separated by <a href=
"#term-whitespace" shape="rect">white space</a> is a legal
expansion.</p>
<p>A legal expansion surrounded by parentheses ('(' and ')') is a
legal expansion.</p>
<pre class="abnf" xml:space="preserve">
this is a test           // sequence of tokens
$action $object          // sequence of rule references
the $object is $color    // sequence of tokens and rule references
(fly to $city)           // parentheses for encapsulation
</pre>
<h5>Special cases</h5>
<p>An empty parenthetical is legal as is a parenthetical containing
only <a href="#term-whitespace" shape="rect">white space</a>; e.g.
'()' or '( )'. Both forms are equivalent to <a href="#S2.2.3"
shape="rect">$NULL</a> and a grammar processor will behave as if
the parenthetical were not present.</p>
<pre class="abnf" xml:space="preserve">
// equivalent sequences
phone home
phone ( ) home
</pre>
<h4 id="id-S2.3-xml">XML Form</h4>
<p>A sequence of XML rule expansion elements (
<code>&lt;ruleref&gt;</code>, <code>&lt;item&gt;</code>,
<code>&lt;one-of&gt;</code>, <code>&lt;token&gt;</code>
<code>&lt;tag&gt;</code>) and CDATA sections containing space
separated tokens must be recognized in temporal sequence. (The only
exception is where one or more "item" elements appear within a
<a href="#S2.4" shape="rect"><code>one-of</code></a> element.)</p>
<p>An <code>item</code> element can surround any expansion to
permit a <a href="#S2.5" shape="rect">repeat</a> attribute or
<a href="#S2.7" shape="rect">language identifier</a> to be
attached. The <code>weight</code> attribute of <code>item</code> is
ignored unless the element appears within a <code>one-of</code>
element.</p>
<pre class="xml" xml:space="preserve">
&lt;!-- sequence of tokens --&gt;
this is a test

&lt;!--sequence of rule references--&gt;
&lt;ruleref uri="#action"/&gt; &lt;ruleref uri="#object"/&gt;

&lt;!--sequence of tokens and rule references--&gt;
the &lt;ruleref uri="#object"/&gt; is &lt;ruleref uri="#color"/&gt;

&lt;!-- sequence container --&gt;
&lt;item&gt;fly to &lt;ruleref uri="#city"/&gt; &lt;/item&gt;
</pre>
<h5>Special cases</h5>
<p>An empty item element is legal as is an item element containing
only <a href="#term-whitespace" shape="rect">white space</a>. Both
forms are equivalent to a <a href="#S2.2.3" shape="rect">NULL</a>
reference and a grammar processor will behave as if the item were
not present.</p>
<pre class="xml" xml:space="preserve">
&lt;!-- equivalent sequences --&gt;
phone home
phone &lt;item/&gt; home
phone &lt;item&gt;&lt;/item&gt; home
phone &lt;item&gt;    &lt;/item&gt; home
</pre></blockquote>
<h3 id="id-S2.4"><a id="S2.4" name="S2.4" shape="rect">2.4
Alternatives</a></h3>
<p>Any set of <em>alternative legal rule expansions</em> is itself
a <a href="#S2" shape="rect">legal rule expansion</a>. For input to
match a set of alternative rule expansions it must match one of the
set of alternative expansions. A set of alternatives must contain
one or more alternatives.</p>
<p>Any set of alternatives may be labeled with a <a href="#S2.7"
shape="rect">language attachment</a>. In the XML Form an <a href=
"#S2.7-xml" shape="rect"><code>xml:lang</code></a> attribute is
present on the <code>one-of</code> element. In the ABNF Form to
ensure correct precedence the set of alternatives must be <a href=
"#S2.3" shape="rect">delimited</a> by parentheses with the <a href=
"#S2.7-abnf" shape="rect">ABNF language attachment</a> immediately
following.</p>
<h4 id="id-S2.4.1"><a id="S2.4.1" name="S2.4.1" shape="rect">2.4.1
Weights</a></h4>
<p>A weight may be optionally provided for any number of
alternatives in an alternative expansion. Weights are simple
positive floating point values without exponentials. Legal formats
are <code>"n"</code>, <code>"n."</code>, <code>".n"</code> and
<code>"n.n"</code> where <code>"n"</code> is a sequence of one or
many digits.</p>
<p>A weight is nominally a multiplying factor in the likelihood
domain of a speech recognition search. A weight of 1.0 is
equivalent to providing no weight at all. A weight greater than
"1.0" positively biases the alternative and a weight less than
"1.0" negatively biases the alternative.</p>
<p><a href="#ref-jel98" shape="rect">[JEL98]</a> and <a href=
"#ref-rab93" shape="rect">[RAB93]</a> are informative references on
the topic of speech recognition technology and the underlying
statistical framework within which weights are applied.</p>
<p>Grammar authors and speech recognizer developers should be aware
of the following limitations upon the definition and application of
weights as outlined above.</p>
<ul>
<li>The application of weights to a speech recognition search is
under the internal control of the recognizer. There is no normative
or informative algorithm for applying weights. Furthermore, speech
recognition is a statistical process so consistent behavior cannot
be guaranteed.</li>
<li>Appropriate weights are difficult to determine for any specific
grammar and recognizer. Guessing weights does not always improve
speech recognition performance.</li>
<li>Effective weights are best obtained by study of real speech
input to a grammar. For example, a reasonable technique for
developing portable weights is to use weights that are correlated
with the occurrence counts of a set of alternatives.</li>
<li>Tuning weights for a particular recognizer does not guarantee
improved recognition performance on other speech recognizers.</li>
</ul>
<blockquote>
<h4 id="id-S2.4-abnf">ABNF Form</h4>
<p>A set of alternative choices is identified as a list of legal
expansions separated by the vertical bar symbol. If necessary, the
set of alternative choices may be delimited by parentheses.</p>
<pre class="abnf" xml:space="preserve">
Michael | Yuriko | Mary | Duke | $otherNames
(1 | 2 | 3)
</pre>
<p>A <a href="#S2.4.1" shape="rect"><code>weight</code></a> is
surrounded by forward slashes and placed before each item in the
alternatives list.</p>
<pre class="abnf" xml:space="preserve">
/10/ small | /2/ medium |  large
/3.1415/ pie | /1.414/ root beer | /.25/ cola
</pre>
<h5>Special Cases</h5>
<p>It is legal for an alternative to be a reference to <a href=
"#S2.2.3" shape="rect">$NULL</a>, an empty parenthetical or a
single tag. In each case the input is equivalent to matching $NULL
and as a result the other alternatives are optional.</p>
<pre class="abnf" xml:space="preserve">
// Legal
$rule1 = word | $NULL;
$rule2 = () | word;
$rule3 = word | {<a href="#S1.4" shape="rect">TAG-CONTENT</a>};
</pre>
<p>An empty alternative (<a href="#term-whitespace" shape=
"rect">white space</a> only) is not legal.</p>
<pre class="abnf" xml:space="preserve">
// ILLEGAL
$rule1 = a | | b;
$rule2 = | b;
$rule3 = a |;
</pre>
<p>The following construct is interpreted as a single weighted
alternative.</p>
<pre class="abnf" xml:space="preserve">
// Legal
$rule1 = /2/ word;
$rule2 = /2/ {<a href="#S1.4" shape="rect">TAG-CONTENT</a>};
$rule3 = /2/ $NULL;
</pre>
<h4 id="id-S2.4-xml">XML Form</h4>
<p>The <code>one-of</code> element identifies a set of alternative
elements. Each alternative expansion is contained in a
<code>item</code> element. There must be at least one
<code>item</code> element contained within a <code>one-of</code>
element. <a href="#S2.4.1" shape="rect">Weights</a> are optionally
indicated by the <code>weight</code> attribute on the
<code>item</code> element.</p>
<pre class="xml" xml:space="preserve">
&lt;one-of&gt;
  &lt;item&gt;Michael&lt;/item&gt;
  &lt;item&gt;Yuriko&lt;/item&gt;
  &lt;item&gt;Mary&lt;/item&gt;
  &lt;item&gt;Duke&lt;/item&gt;
  &lt;item&gt;&lt;ruleref uri="#otherNames"/&gt;&lt;/item&gt;
&lt;/one-of&gt;

&lt;one-of&gt;&lt;item&gt;1&lt;/item&gt; &lt;item&gt;2&lt;/item&gt; &lt;item&gt;3&lt;/item&gt;&lt;/one-of&gt;

&lt;one-of&gt;
  &lt;item weight="10"&gt;small&lt;/item&gt;
  &lt;item weight="2"&gt;medium&lt;/item&gt;
  &lt;item&gt;large&lt;/item&gt;
&lt;/one-of&gt;

&lt;one-of&gt;
  &lt;item weight="3.1415"&gt;pie&lt;/item&gt;
  &lt;item weight="1.414"&gt;root beer&lt;/item&gt;
  &lt;item weight=".25"&gt;cola&lt;/item&gt;
&lt;/one-of&gt;
</pre>
<h5>Special cases</h5>
<p>A <code>one-of</code> element containing a single item is legal
and requires that input match the single item. The single item may
be optionally weighted.</p>
<pre class="xml" xml:space="preserve">
&lt;one-of&gt;
  &lt;item&gt;word&lt;/item&gt;
&lt;/one-of&gt;

&lt;one-of&gt;
  &lt;item weight="2.0"&gt;word&lt;/item&gt;
&lt;/one-of&gt;
</pre>
<p>Is it legal for an alternative to be a reference to <a href=
"#S2.2.3" shape="rect">NULL</a>, an empty item or a single tag. In
each case the input is equivalent to matching NULL and as a result
the other alternatives are optional.</p>
<pre class="xml" xml:space="preserve">
&lt;one-of&gt;
  &lt;item&gt;word&lt;/item&gt;
  &lt;item/&gt;
&lt;/one-of&gt;
&lt;one-of&gt;
  &lt;item&gt;word&lt;/item&gt;
  
  <span>&lt;item&gt; &lt;ruleref special="NULL"/&gt; &lt;/item&gt;</span>
&lt;/one-of&gt;
&lt;one-of&gt;
  &lt;item&gt;word&lt;/item&gt;
  &lt;item&gt; &lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT</a>&lt;/tag&gt; &lt;/item&gt;
&lt;/one-of&gt;
</pre></blockquote>
<h3 id="id-S2.5"><a id="S2.5" name="S2.5" shape="rect">2.5
Repeats</a></h3>
<p>Any <em>repeated legal rule expansion</em> is itself a <a href=
"#S2" shape="rect">legal rule expansion</a>.</p>
<p>Operators are provided that define a legal rule expansion as
being another sub-expansion that is optional, that is repeated zero
or more times, that is repeated one or more times, or that is
repeated some range of times.</p>
<table border="1" cellpadding="3" summary=
"Legal Values for Repeat Attribute">
<tr>
<td align="center" colspan="1" rowspan="1"><b><em>ABNF
Form</em><br clear="none" />
Example</b></td>
<td align="center" colspan="1" rowspan="1"><b><em>XML
Form</em><br clear="none" />
Example</b></td>
<td colspan="1" rowspan="1"><b>Behavior</b></td>
</tr>
<tr>
<td align="center" colspan="1" rowspan="1">
<em>&lt;n&gt;</em><br clear="none" />
&lt;6&gt;</td>
<td align="center" colspan="1" rowspan="1">
<em>repeat="n"</em><br clear="none" />
repeat="6"</td>
<td colspan="1" rowspan="1">The contained expansion is repeated
exactly "n" times. "n" must be "0" or a positive integer.</td>
</tr>
<tr>
<td align="center" colspan="1" rowspan="1">
<em>&lt;m-n&gt;</em><br clear="none" />
&lt;4-6&gt;</td>
<td align="center" colspan="1" rowspan="1">
<em>repeat="m-n"</em><br clear="none" />
repeat="4-6"</td>
<td colspan="1" rowspan="1">The contained expansion is repeated
between "m" and "n" times (inclusive). "m" and "n" must both be "0"
or a positive integer and "m" must be less than or equal to
"n".</td>
</tr>
<tr>
<td align="center" colspan="1" rowspan="1">
<em>&lt;m-&gt;</em><br clear="none" />
&lt;3-&gt;</td>
<td align="center" colspan="1" rowspan="1">
<em>repeat="m-"</em><br clear="none" />
repeat="3-"</td>
<td colspan="1" rowspan="1">The contained expansion is repeated "m"
times or more (inclusive). "m" must be "0" or a positive integer.
For example, "3-" declares that the contained expansion can occur
three, four, five or more times.</td>
</tr>
<tr>
<td align="center" colspan="1" rowspan="1">&lt;0-1&gt;<br clear=
"none" />
[...]</td>
<td align="center" colspan="1" rowspan="1">repeat="0-1"</td>
<td colspan="1" rowspan="1">The contained expansion is
optional.</td>
</tr>
</table>
<h5>Common Repeats</h5>
<p>As indicated in the table above, an expansion that can occur 0-1
times is optional. Because optionality is such a common form the
ABNF syntax provides square brackets as a special operator for
representing optionality.</p>
<p>A repeat of "0-" indicates that an expansion can occur zero
times, once or any number of multiple times. In regular expression
languages this is often represented by the <em>Kleene star</em>
('*') which is reserved but not used in ABNF.</p>
<p>A repeat of "1-" indicates that an expansion can occur once or
any number of multiple times. In regular expression languages this
is often represented by the <em>positive closure</em> ('+') which
is reserved but not used in ABNF.</p>
<p>Although both ABNF and XML support a grammar that permits an
unbounded number of input tokens it is not the case that users will
speak indefinitely. Speech recognition can perform more effectively
if the author indicates a more limited range of repeat
occurrences.</p>
<h5>Special Cases</h5>
<p>Where a number of possible repetitions (e.g. &lt;m-&gt; or
&lt;m-n&gt; (n &gt; 0) but not &lt;0&gt;) is expressed on a
construct whose only content is one or more <a href="#S2.6" shape=
"rect">tag</a> elements, the behavior of the grammar processor is
not defined and will be specific to individual implementations.</p>
<p>Any number of non-optional repetitions (e.g., &lt;m-n&gt;;
m&gt;0) of <a href="#S2.2.3" shape="rect">VOID</a> is equivalent to
a single <a href="#S2.2.3" shape="rect">VOID</a>.</p>
<p>The behavior of a grammar processor in handling any number of
repetitions of <a href="#S2.2.3" shape="rect">NULL</a> is not
defined and will be specific to individual implementations.</p>
<p>If the number of repetitions for any expansion can be only zero
(i.e. &lt;0&gt; or &lt;0-0&gt;) then the expansion is equivalent to
<a href="#S2.2.3" shape="rect">NULL</a>.</p>
<h4 id="id-S2.5.1"><a id="S2.5.1" name="S2.5.1" shape="rect">2.5.1
Repeat Probabilities</a></h4>
<p>Any repeat operator may specify an optional repeat probability.
The value indicates the probability of successive repetition of the
repeated expansion.</p>
<p>A repeat probability value must be in the floating pointing
range of "0.0" to "1.0" (inclusive). Values outside this range are
illegal. The floating point format is one of "n", "n.", "n.nnnn",
".nnnn" (with any number of digits after the dot).</p>
<p>Note: repeat probabilities and <a href="#S2.4.1" shape=
"rect">weights</a> are different logical entities and have a
different impact upon a speech recognition search.</p>
<p>Informative example: A simple example is an optional expansion
(zero or one occurrences) with a probability &mdash; say "0.6". The
grammar indicates that the chance that the expansion will be
matched is 60% and that the chance that the expansion will not be
present is 40%.</p>
<p>When no maximum is specified in a range (m-) the probabilities
decay exponentially.</p>
<p>Grammar authors and speech recognizer developers should be aware
of the following limitations upon the definition and application of
repeat probabilities as outlined above.</p>
<ul>
<li>The application of repeat probabilities to a speech recognition
search is under the internal control of the recognizer. There is no
specified algorithm for applying repeat probabilities in a speech
recognition processor so consistent behavior cannot be
guaranteed.</li>
<li>Appropriate repeat probabilities are often difficult to
determine for any specific grammar and recognizer. Guessing repeat
probabilities does not always improve speech recognition
performance.</li>
<li>Appropriate repeat probabilities are best obtained by study of
statistical patterns of real speech input. Tuning repeat
probabilities for a particular recognizer does not guarantee
improved recognition performance on other speech recognizers.</li>
</ul>
<p>Useful references on statistical models of speech recognition
include <a href="#ref-jel98" shape="rect">[JEL98]</a> and <a href=
"#ref-rab93" shape="rect">[RAB93]</a>.</p>
<blockquote>
<h4 id="id-S2.5-abnf">ABNF Form</h4>
<p>The following are postfix operators: <code>&lt;m-n&gt;
&lt;m-&gt; &lt;m&gt;</code>. A postfix operator is logically
attached to the preceding expansion. Postfix operators have high
precedence and so are tightly bound to the immediately preceding
expansion (see <a href="#S2.8" shape="rect">Section 2.8</a>).</p>
<p>Optional expansions may be delimited by square brackets:
<code>[expansion]</code>. Alternatively, an optional expansion is
indicated by the postfix operator "<code>&lt;0-1&gt;</code>".</p>
<p>The following symbols are <em>reserved</em> for future use in
ABNF: '*', '+', '?'. These symbols must not be used at any place in
a grammar where the syntax currently permits a repeat operator.</p>
<pre class="abnf" xml:space="preserve">
// the token "very" is optional
[very]
very &lt;0-1&gt;

// the rule reference $digit can occur zero, one or many times

$digit &lt;0-&gt;

// the rule reference $digit can occur one or more times

$digit &lt;1-&gt;

// the rule reference $digit can occur four, five or six times
$digit &lt;4-6&gt;

// the rule reference $digit can occur ten or more times
$digit &lt;10-&gt;

// Examples of the following expansion
//   "pizza"
//   "big pizza with pepperoni"
//   "very big pizza with cheese and pepperoni"
[[very] big] pizza ([with | and] $topping) &lt;0-&gt;
</pre>
<p>Repeat probabilities are only supported in the range form. The
probability is delimited by slash characters and contained within
the angle brackets: <code>&lt;m-n /prob/&gt;</code> and
<code>&lt;m- /prob/&gt;</code>.</p>
<pre class="abnf" xml:space="preserve">
// the token "very" is optional and is 60% likely to occur
// and 40% likely to be absent in input
very &lt;0-1 /0.6/&gt;

// the rule reference $digit must occur two to four times 
// with 80% probability of recurrence
$digit &lt;2-4 /.8/&gt;
</pre>
<h4 id="id-S2.5-xml">XML Form</h4>
<p>The <code>item</code> element has a <code>repeat</code>
attribute that indicates the number of times the contained
expansion may be repeated. The following example illustrates the
accepted values of the attribute.</p>
<pre class="xml" xml:space="preserve">
&lt;!-- the token "very" is optional --&gt;

&lt;item repeat="0-1"&gt;very&lt;/item&gt;

&lt;!-- the rule reference to digit can occur zero, one or many times --&gt;

&lt;item repeat="0-"&gt; &lt;ruleref uri="#digit"/&gt; &lt;/item&gt;

&lt;!-- the rule reference to digit can occur one or more times --&gt;

&lt;item repeat="1-"&gt; &lt;ruleref uri="#digit"/&gt; &lt;/item&gt;

&lt;!-- the rule reference to digit can occur four, five or six times --&gt;
&lt;item repeat="4-6"&gt; &lt;ruleref uri="#digit"/&gt; &lt;/item&gt;

&lt;!-- the rule reference to digit can occur ten or more times --&gt;
&lt;item repeat="10-"&gt; &lt;ruleref uri="#digit"/&gt; &lt;/item&gt;

&lt;!-- Examples of the following expansion --&gt;
&lt;!--   "pizza" --&gt;
&lt;!--   "big pizza with pepperoni" --&gt;
&lt;!--   "very big pizza with cheese and pepperoni" --&gt;

&lt;item repeat="0-1"&gt; 
   &lt;item repeat="0-1"&gt; very &lt;/item&gt;
   big 
&lt;/item&gt; 
pizza
&lt;item repeat="0-"&gt;
   &lt;item repeat="0-1"&gt;
      &lt;one-of&gt;
         &lt;item&gt;with&lt;/item&gt;
         &lt;item&gt;and&lt;/item&gt;
      &lt;/one-of&gt;
   &lt;/item&gt;
   &lt;ruleref uri="#topping"/&gt;
&lt;/item&gt;
</pre>
<p>The <code>repeat-prob</code> on the item element carries the
repeat probability. Repeat probabilities are supported on any item
element but are ignored if the repeat attribute is not also
specified.</p>
<pre class="xml" xml:space="preserve">
&lt;-- The token "very" is optional and is 60% likely to occur. --&gt;
&lt;-- Means 40% chance that "very" is absent in input --&gt;
&lt;item repeat="0-1" repeat-prob="0.6"&gt;very&lt;/item&gt;

&lt;-- The rule reference to digit must occur two to four times --&gt;
&lt;-- with 80% probability of recurrence. --&gt;
&lt;item repeat="2-4" repeat-prob=".8"&gt;
   &lt;ruleref uri="#digit"/&gt; 
&lt;/item&gt;
</pre></blockquote>
<h3 id="id-S2.6"><a id="S2.6" name="S2.6" shape="rect">2.6
Tags</a></h3>
<p>A <em>tag</em> is a <a href="#S2" shape="rect">legal rule
expansion</a> <span>(a tag can also be declared in the grammar
header - see <a href="#S4.1" shape="rect">S4.1</a>)</span>.</p>
<p>A <code>tag</code> is an <em>arbitrary string</em> that may be
included inline within any legal rule expansion. Any number of tags
may be included inline within a rule expansion.</p>
<p>Tags do not affect the legal word patterns defined by the
grammars or the process of recognizing speech or other input given
a grammar.</p>
<p>Tags may contain content for <a href="#S1.4" shape=
"rect">semantic interpretation</a>. The semantic interpretation
processes may affect the recognition result.</p>
<p><a href="#S2.7" shape="rect">Language attachments</a> have no
effect upon tags.</p>
<p>The <a href="#S4.8" shape="rect">tag format declaration</a>
indicates the content type of all tags in a grammar.</p>
<h5>Special Cases</h5>
<p>It is legal to use a <code>tag</code> as a stand-alone
expansion. For example, a rule may expand to a single tag and no
tokens.</p>
<pre class="abnf" xml:space="preserve">
  $rule = {<a href="#S1.4" shape="rect">TAG-CONTENT</a>};
</pre>
<pre class="xml" xml:space="preserve">
  &lt;rule id="rule"&gt;&lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT</a>&lt;/tag&gt;&lt;/rule&gt;
</pre>
<blockquote>
<h4 id="id-S2.6-abnf">ABNF Form</h4>
<p>A <code>tag</code> is delimited by either a pair of opening and
closing curly brackets &mdash; '{' and '}' &mdash; or by the following
3-character sequences which are considered very unlikely to occur
within a tag &mdash; '{!{' and '}!}'. A tag delimited by single curly
brackets cannot contain the single closing curly bracket character
('}'). A tag delimited by the 3-character sequence cannot contain
the closing 3-character sequence ('}!}').</p>
<p>The tag content is all text between the opening and closing
character sequences including leading and trailing <a href=
"#term-whitespace" shape="rect">white space</a>. The contents of the
tag are not parsed by the grammar processor.</p>
<p>Tag precedence is the same as for rule references and tokens. In
the first example below there is a sequence of six space-separated
expansions (3 tokens, a tag, a token and a tag). In the second
example, the alternative is a choice between a sequence containing
a token and a tag or a sequence containing a rule reference and a
tag.</p>
<pre class="abnf" xml:space="preserve">
$rule1 = this is a {<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>} test {<a href="#S1.4" shape=
"rect">TAG-CONTENT-2</a>};

$rule2 = open {<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>} | $close {<a href="#S1.4" shape=
"rect">TAG-CONTENT-2</a>};

$rule3 = {!{ a simple tag containing { and } needs no escaping }!};
</pre>
<h4 id="id-S2.6-xml">XML Form</h4>
<p>A <code>tag</code> element can be a direct child of the
<code>item</code> and <code>rule</code> elements. The content of
<code>tag</code> is CDATA.</p>
<pre class="xml" xml:space="preserve">
&lt;rule id="rule1"&gt;this is a &lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>&lt;/tag&gt; test &lt;tag&gt;<a href=
"#S1.4" shape="rect">TAG-CONTENT-2</a>&lt;/tag&gt; &lt;/rule&gt;

&lt;rule id="rule2"&gt;
   &lt;one-of&gt;
      &lt;item&gt; open &lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>&lt;/tag&gt; &lt;/item&gt;
      &lt;item&gt; &lt;ruleref uri="#close"/&gt; &lt;tag&gt;<a href="#S1.4"
   shape="rect">TAG-CONTENT-2</a>&lt;/tag&gt; &lt;/item&gt;
   &lt;/one-of&gt;
&lt;/rule&gt;
</pre></blockquote>
<h3 id="id-S2.7"><a id="S2.7" name="S2.7" shape="rect">2.7
Language</a></h3>
<p>Any <a href="#S2" shape="rect">legal rule expansion</a> that has
an attached <a href="#term-language" shape="rect">language
identifier</a> is itself a legal rule expansion. Both the ABNF Form
and the XML Form permit a legal language identifier to be attached
to any <a href="#S2.1" shape="rect">token</a>, <a href="#S2.3"
shape="rect">sequence</a> or <a href="#S2.4" shape="rect">set of
alternatives</a> <span>(Note that <a href="#S2.2" shape="rect">rule
reference</a> does not permit a language identifier to be
attached)</span>. The syntax for the <a href="#S2.7-abnf" shape=
"rect">ABNF Form</a> and for the <a href="#S2.7-xml" shape=
"rect">XML Form</a> are provided below.</p>
<p>The language declaration for a rule expansion affects only the
contained content. Moreover, the language declaration affects only
the handling of <a href="#S2.1" shape="rect">tokens</a> in the
contained content and does not affect <a href="#S2.6" shape=
"rect">tags</a> or <a href="#S2.2" shape="rect">rule
references</a>. The application of language to token handling and
particularly to pronunciation lookup is described in <a href=
"#S2.1" shape="rect">Section 2.1</a>.</p>
<p>By default a grammar is a single language document with a
<a href="#term-language" shape="rect">language identifier</a>
provided in the <a href="#S4.5" shape="rect">language
declaration</a> in the <a href="#S4.1" shape="rect">grammar
header</a> (see <a href="#S4.5" shape="rect">Section 4.5</a>). All
tokens within that grammar, unless otherwise declared, will be
handled according to the grammar's language.</p>
<p>In situations where applications target a multilingual user
community, grammars that contain words in more than one language
may be needed. For example, in response to a prompt such as:
<em>"Do you want to talk to Andr&eacute; Pr&eacute;vost?"</em> (a
combination of an English sentence with a French name), the
response may be either <em>"yes"</em> or <em>"oui"</em>.</p>
<p>The Speech Recognition Grammar Specification permits one grammar
to collect input from more than one language. The specification
also permits multiple grammars each with a separate single language
to be used in parallel. The specification also permits a single
input utterance to contain more than one language. Finally, the
specification permits any combination of the above: for example,
parallel grammars each with multi-lingual capability.</p>
<p>Not all user agents are required to support all languages, or
indeed any or all of the multi-lingual capabilities. The
conformance requirements regarding multi-lingual support for XML
Form grammar processors and ABNF Form grammar processors are the
same and are laid out in <a href="#S5.4" shape="rect">Section
5.4</a> and <a href="#S5.6" shape="rect">Section 5.6</a>
respectively.</p>
<p>There is a related challenge for multilingual applications that
deal with proper names (people, streets, companies, etc.) that may
be spoken with different pronunciations or accents depending upon
the language of origin and the speaking language. It is often
impossible to predict the language that users will use to pronounce
certain tokens. In fact, users may actually use different languages
for different words in the same sentence, and in unpredictable
ways. For instance, the name "Robert Jones" might be pronounced by
a French-speaking user using the French pronunciation for "Robert"
but an English pronunciation for "Jones", whereas a mono-lingual
English speaker would use the English pronunciation for both
words.</p>
<p><em>Language scoping:</em> language declarations are scoped
locally to a document and to a rule definition. In XML terminology,
the language attribute is inherited down the document tree. Where a
language change encompasses a reference to another grammar, the
referenced rule and its containing grammar define the language of
the reference expansion. The language in effect at the point of the
rule reference does not have any effect upon the referenced
rule.</p>
<p><em>Language and results:</em> The language used in the
recognition of a token is not considered a part of the speech
result even in the case that a language declaration is associated
with a token.</p>
<blockquote>
<h4 id="id-S2.7-abnf"><a id="S2.7-abnf" name="S2.7-abnf" shape=
"rect">ABNF Form</a></h4>
<p>In the ABNF Form a <a href="#term-language" shape=
"rect">language identifier</a> may be right-attached to any
<a href="#S2" shape="rect">legal rule expansion</a> <span>except
<a href="#S2.2" shape="rect">rule reference</a></span>. The
attachment is an exclamation point character ('!') followed by a
legal language identifier without intervening <a href=
"#term-whitespace" shape="rect">white space</a>.</p>
<p>The language attachment has higher <a href="#S2.8" shape=
"rect">precedence</a> than <a href="#S2.3" shape=
"rect">sequences</a> or <a href="#S2.4" shape=
"rect">alternatives</a>. To attach a language to these rule
expansion types the expansion should be delimited by parentheses
(see <a href="#S2.3" shape="rect">Section 2.3</a>).</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

// Default grammar language is US English
language en-US;

// Single language attachment to tokens
// Note that "fr-CA" (Canadian French) is applied to only
//  the word "oui" because of precedence rules
$yes = yes | oui!fr-CA;

// Single language attachment to an expansion
$people1 = (Michel Tremblay | Andr&eacute; Roy)!fr-CA;

// Handling language-specific pronunciations of the same word
// A capable speech recognizer will listen for Mexican Spanish and
//   US English pronunciations.
$people2 = Jose!en-US; | Jose!es-MX;

/**
 * Multi-lingual input possible
 * @example may I speak to Andr&eacute; Roy
 * @example may I speak to Jose
 */
public $request = may I speak to ($people1 | $people2);
</pre>
<h4 id="id-S2.7-xml"><a id="S2.7-xml" name="S2.7-xml" shape=
"rect">XML Form</a></h4>
<p>XML 1.0 <a href="#ref-xml" shape="rect">[XML &sect;2.12]</a>
defines the <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-lang-tag" shape=
"rect"><code>xml:lang</code></a> attribute for language
identification. The attribute provides a single <a href=
"#term-language" shape="rect">language identifier</a> for the
content of the element on which it appears. The
<code>xml:lang</code> attribute may be attached to <a href="#S2.4"
shape="rect"><code>one-of</code></a> , <a href="#S2.1" shape=
"rect"><code>token</code></a> and <a href="#S2.3" shape=
"rect"><code>item</code></a>. It applies the token handling of
scoped tokens.</p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;
 
&lt;!-- the default grammar language is US English --&gt;
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en-US" version="1.0"&gt;
 
  &lt;!-- 
     single language attachment to tokens
     "yes" inherits US English language
     "oui" is Canadian French language
  --&gt;
  &lt;rule id="yes"&gt;
    &lt;one-of&gt;
      &lt;item&gt;yes&lt;/item&gt;
      &lt;item xml:lang="fr-CA"&gt;oui&lt;/item&gt;
    &lt;/one-of&gt; 
  &lt;/rule&gt; 
  
  &lt;!-- Single language attachment to an expansion --&gt;
  &lt;rule id="people1"&gt;
    &lt;one-of xml:lang="fr-CA"&gt;
      &lt;item&gt;Michel Tremblay&lt;/item&gt;
      &lt;item&gt;Andr&eacute; Roy&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
  
  &lt;!--
     Handling language-specific pronunciations of the same word
     A capable speech recognizer will listen for Mexican Spanish 
     and US English pronunciations.
  --&gt;
  &lt;rule id="people2"&gt;
    &lt;one-of&gt;
      &lt;item xml:lang="en-US"&gt;Jose&lt;/item&gt;
      &lt;item xml:lang="es-MX"&gt;Jose&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
  
  &lt;!-- Multi-lingual input is possible --&gt;
  &lt;rule id="request" scope="public"&gt;
    &lt;example&gt; may I speak with Andr&eacute; Roy &lt;/example&gt;
    &lt;example&gt; may I speak with Jose &lt;/example&gt;
  
    may I speak with
    &lt;one-of&gt;
      &lt;item&gt; &lt;ruleref uri="#people1"/&gt; &lt;/item&gt;
      &lt;item&gt; &lt;ruleref uri="#people2"/&gt; &lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt;
</pre></blockquote>
<h3 id="id-S2.8"><a id="S2.8" name="S2.8" shape="rect">2.8
Precedence</a></h3>
<p>This section defines the precedence of the ABNF rule expansion
syntax. Because XML documents explicitly indicate structure there
is no ambiguity and thus a precedence definition is not required.
The precedence definitions for the ABNF Form are intended to
minimize the need for parentheses.</p>
<blockquote>
<h4 id="id-S2.8-abnf">ABNF Form</h4>
<p>The following is the ordering of precedence of rule expansions.
Parentheses may be used to explicitly control rule structure.</p>
<ol>
<li><a href="#S2.2" shape="rect">A rule reference</a>, a <a href=
"#S2.1" shape="rect">quoted token</a>, an <a href="#S2.1" shape=
"rect">unquoted token</a> or a <a href="#S2.6" shape=
"rect">tag</a>.</li>
<li><a href="#S2.3" shape="rect">Parentheses</a> ('(' and ')') for
grouping and square brackets ('[' and ']') for <a href="#S2.5"
shape="rect">optional grouping</a>.</li>
<li><a href="#S2.5" shape="rect">Repeat operator</a> (e.g.
"<code>&lt;0-1&gt;</code>") and <a href="#S2.7" shape=
"rect">language attachment</a> (e.g. "!en-AU") apply to the
tightest immediate preceding rule expansion. (To apply them to a
sequence or to alternatives, use `()' or `[]' for grouping.)</li>
<li><a href="#S2.3" shape="rect">Sequence</a> of rule
expansions.</li>
<li>Set of <a href="#S2.4" shape="rect">alternative rule
expansions</a> separated by vertical bars ('|') with optional
<a href="#S2.4.1" shape="rect">weights</a>.</li>
</ol>
<h4 id="id-S2.8-xml">XML Form</h4>
<p>None required. XML structure is explicit.</p>
</blockquote>
<h2 id="id-S3"><a id="S3" name="S3" shape="rect">3. Rule
Definitions</a></h2>
<ul>
<li class="tocline">3.1 <a href="#S3.1" shape="rect">Basic Rule
Definition</a></li>
<li class="tocline">3.2 <a href="#S3.2" shape="rect">Scoping of
Rule Definitions</a></li>
<li class="tocline">3.3 <a href="#S3.3" shape="rect">Example
Phrases</a></li>
</ul>
<p>A <em>rule definition</em> associates a legal <a href="#S2"
shape="rect">rule expansion</a> with a <em>rulename</em>. The rule
definition is also responsible for defining the <a href="#S3.2"
shape="rect"><em>scope</em></a> of the rule definition: whether it
is local to the grammar in which it is defined or whether it may be
referenced within other grammars. Finally, the rule definition may
additionally include documentation comments and other
pragmatics.</p>
<p>The rulename for each rule definition must be unique within a
grammar. The same rulename may be used in multiple grammars.</p>
<p>A rule definition is referenced by a URI in a <a href="#S2.2"
shape="rect">rule reference</a> with the rulename being represented
as the fragment identifier.</p>
<h3 id="id-S3.1"><a id="S3.1" name="S3.1" shape="rect">3.1 Basic
Rule Definition</a></h3>
<p>The core purpose of a rule definition is to associate a legal
rule expansion with a rulename.</p>
<p>A legal rulename in either the XML Form or ABNF Form is a
character sequence that:</p>
<ul>
<li>is an <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#NT-Name" shape=
"rect">XML Name</a> <a href="#ref-xml" shape="rect">[XML
&sect;2.3]</a>,</li>
<li>and does not contain the following character '.', ':',
'-',</li>
<li>and is not the name of a <a href="#S2.2.3" shape="rect">special
rule</a> ("NULL", "VOID", "GARBAGE").</li>
</ul>
<p>Defined rulenames must be unique within a grammar. The <a href=
"#AppC" shape="rect">schema</a> enforces this by declaring the
rulename as an XML ID.</p>
<p>Rulenames are case-sensitive in both XML and ABNF grammars.
Exact string comparison is used to resolve rulename references.</p>
<p>A legal rulename cannot be one of the <a href="#S2.2.3" shape=
"rect">special rules</a>: specifically "NULL", "VOID" or
"GARBAGE".</p>
<blockquote>
<h4 id="id-S3.1-abnf">ABNF Form</h4>
<p>The rule definition consists of an optional scoping declaration
(explained in the next section) followed by a legal rule name, an
equals sign, a legal rule expansion and a closing semicolon. The
rule definition has one of the following legal forms:</p>
<pre class="abnf" xml:space="preserve">
<em>$ruleName = ruleExpansion;</em>
public <em>$ruleName = ruleExpansion;</em>
private <em>$ruleName = ruleExpansion;</em>
</pre>
<p>For example:</p>
<pre class="abnf" xml:space="preserve">
$city = Boston | "New York" | Madrid;
$command = $action $object;
</pre>
<h5>Special Cases</h5>
<p>An empty rule definition is illegal.</p>
<p>It is legal to define a rule that expands to empty parentheses
or <a href="#S2.2.3" shape="rect">$NULL</a> (equivalent forms). It
is legal to define a rule that expands to a single
<code>tag</code>.</p>
<pre class="abnf" xml:space="preserve">
// Legal
$rule = ();
$rule = $NULL;
$rule = {<a href="#S1.4" shape="rect">TAG-CONTENT</a>};

// ILLEGAL
$rule = ;
</pre>
<h4 id="id-S3.1-xml">XML Form</h4>
<p>A rule definition is represented by the <code>rule</code>
element. The <code>id</code> attribute of the element indicates the
name of the rule and must be unique within the grammar (this is
enforced by XML). The contents of the <code>rule</code> element may
be any legal rule expansion defined in <a href="#S2" shape=
"rect">Section 2</a>. The <code>scope</code> attribute is explained
in the next section.</p>
<pre class="xml" xml:space="preserve">
&lt;rule id="city"&gt;
   &lt;one-of&gt;
      &lt;item&gt;Boston&lt;/item&gt;
      &lt;item&gt;"San Francisco"&lt;/item&gt;
      &lt;item&gt;Madrid&lt;/item&gt; 
   &lt;/one-of&gt;
&lt;/rule&gt;
&lt;rule id="command"&gt;
   &lt;ruleref uri="#action"/&gt;
   &lt;ruleref uri="#object"/&gt;
&lt;/rule&gt;
</pre>
<h5>Special Cases</h5>
<p>It is not legal to define an empty rule element or a rule
element that contains only <a href="#term-whitespace" shape=
"rect">white space</a> CDATA.</p>
<p>It is legal to define a rule that expands to an empty item or to
a single rule reference to <a href="#S2.2.3" shape=
"rect">NULL</a>.</p>
<p>It is legal to define a rule that expands to a single
<code>tag</code> element.</p>
<pre class="abnf" xml:space="preserve">
&lt;!-- Legal --&gt;
&lt;rule id="rule"&gt;&lt;item/&gt;&lt;/rule&gt;
&lt;rule id="rule"&gt;&lt;ruleref special="NULL"/&gt;&lt;/rule&gt;
&lt;rule id="rule"&gt;&lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT</a>&lt;/tag&gt;&lt;/rule&gt;

&lt;!-- ILLEGAL --&gt;
&lt;rule id="rule"/&gt;
&lt;rule id="rule"&gt;&lt;/rule&gt;
&lt;rule id="rule"&gt;   &lt;/rule&gt;
</pre></blockquote>
<h3 id="id-S3.2"><a id="S3.2" name="S3.2" shape="rect">3.2 Scoping
of Rule Definitions</a></h3>
<p>Each defined rule has a scope. The scope is either "private" or
"public". If not explicitly declared in a rule definition then the
scope defaults to "private".</p>
<p><span>A</span> public-scoped rule may be <span>explicitly</span>
<a href="#S2.2" shape="rect">referenced</a> <span>(using the
fragment identifier syntax of a URI)</span> in the rule definitions
of other grammars and in other non-grammar documents<span>.
A</span> private-scoped <span>rule</span> cannot be so referenced
<span>and is directly accessible only within its containing
grammar. A private rule may be explicitly referenced only by other
rules within the same grammar</span>.</p>
<p>Informative: grammar authors may consider the following guidance
when scoping the rules of a grammar.</p>
<ul>
<li>Grammar authoring shares many properties of programming.
Establishing contracts of an API is analogous to defining a set of
grammars and defining the public rules of a grammar each with
defined language behavior.</li>
<li>Consistent design and implementation of public rules promotes
grammar re-use and facilitates creation of grammar libraries.</li>
<li>Natural language grammars often require creation of many
internal "working" rules to create a smaller number of useful
external rules. Hiding working rules with private scope allows
revision of those rules without affecting other grammars that
reference the grammar. Hiding working rules also prevents
accidental mis-use of a working rule.</li>
<li>Grammar compilation resembles programming language compilation.
Making rules private allows advanced grammar compilers to perform
optimizations that cannot be applied when a rule is declared
public.</li>
</ul>
<blockquote>
<h4 id="id-S3.2-abnf">ABNF Form</h4>
<p>A rule definition may be annotated with the keywords "public" or
"private". If no scope is provided, the default is "private".</p>
<pre class="abnf" xml:space="preserve">
$town = Townsville | Beantown;
private $city = Boston | "New York" | Madrid;
public $command = $action $object;
</pre>
<h4 id="id-S3.2-xml">XML Form</h4>
<p>The <code>scope</code> attribute of the <code>rule</code>
element defines the scope of the rule definition. Defined values
are <code>public</code> and <code>private</code>. If omitted, the
default scope is <code>private</code>.</p>
<pre class="xml" xml:space="preserve">
&lt;rule id="town"&gt;
   &lt;one-of&gt;
      &lt;item&gt;Townsville&lt;/item&gt;
      &lt;item&gt;Beantown&lt;/item&gt; 
   &lt;/one-of&gt;
&lt;/rule&gt;
&lt;rule id="city" scope="private"&gt;
   &lt;one-of&gt;
      &lt;item&gt;Boston&lt;/item&gt;
      &lt;item&gt;"San Francisco"&lt;/item&gt;
      &lt;item&gt;Madrid&lt;/item&gt; 
   &lt;/one-of&gt;
&lt;/rule&gt;
&lt;rule id="command" scope="public"&gt;
   &lt;ruleref uri="#action"/&gt;
   &lt;ruleref uri="#object"/&gt;
&lt;/rule&gt;
</pre></blockquote>
<h3 id="id-S3.3"><a id="S3.3" name="S3.3" shape="rect">3.3 Example
Phrases</a></h3>
<p>It is often desirable to include examples of phrases that match
rule definitions along with the definition. Zero, one or many
example phrases may be provided for any rule definition. Because
the examples are explicitly marked, automated tools can be used for
regression testing and for generation of grammar documentation.</p>
<blockquote>
<h4 id="id-S3.3-abnf">ABNF Form</h4>
<p>A <a href="#S4.13" shape="rect">documentation comment</a> is a
C/C++/Java comment that starts with the sequence of characters
<code>/**</code> and which immediately precedes the relevant rule
definition. Zero or more <code>@example</code> tags may be
contained at the end of the documentation comment. The syntax
follows the <a href=
"http://java.sun.com/docs/books/jls/first_edition/html/18.doc.html#25995"
   shape="rect">Tagged Paragraph</a> of a documentation comment of
   the Java Programming Language <a href="#ref-java" shape=
   "rect">[JAVA &sect;18.4]</a>. The tokenization of the example
   follows the tokenization and sequence rules defined in <a href=
   "#S2.1" shape="rect">Section 2.1</a> and <a href="#S2.3" shape=
   "rect">Section 2.3</a> respectively.</p>
<pre class="abnf" xml:space="preserve">
/**
 * A simple directive to execute an action.
 *
 * @example open the window
 * @example close the door
 */
public $command = $action $object;
</pre>
<h4 id="id-S3.3-xml">XML Form</h4>
<p>Any number of "example" elements may be provided as the initial
content within a "rule" element. The tokenization of the example
follows the tokenization and sequence rules defined in <a href=
"#S2.1" shape="rect">Section 2.1</a> and <a href="#S2.3" shape=
"rect">Section 2.3</a> respectively.</p>
<pre class="xml" xml:space="preserve">
&lt;rule id="command" scope="public"&gt;
    &lt;!-- A simple directive to execute an action. --&gt;
    &lt;example&gt; open the window &lt;/example&gt;
    &lt;example&gt; close the door &lt;/example&gt;
    &lt;ruleref uri="#action"/&gt; &lt;ruleref uri="#object"/&gt;
&lt;/rule&gt;
</pre></blockquote>
<h2 id="id-S4"><a id="S4" name="S4" shape="rect">4. Grammar
Documents</a></h2>
<p>A conforming stand-alone grammar document consists of a <a href=
"#S4.1" shape="rect">legal header</a> followed by a body consisting
of a set of legal <a href="#S3" shape="rect">rule definitions</a>.
All rules defined within that grammar are scoped within the
grammar's rulename namespace and each rulename must be <a href=
"#S3" shape="rect">legal and unique</a>.</p>
<p>It is legal for a grammar to define no rules. The grammar cannot
be used for processing input since it defines no patterns for
matching user input.</p>
<ul>
<li class="tocline">4.1 <a href="#S4.1" shape="rect">Grammar Header
Declarations</a></li>
<li class="tocline">4.2 <a href="#S4.2" shape="rect">ABNF
Self-Identifying Header</a></li>
<li class="tocline">4.3 <a href="#S4.3" shape="rect">XML Form
Prolog and Root Element</a></li>
<li class="tocline">4.4 <a href="#S4.4" shape="rect">Character
Encoding</a></li>
<li class="tocline">4.5 <a href="#S4.5" shape=
"rect">Language</a></li>
<li class="tocline">4.6 <a href="#S4.6" shape="rect">Mode</a></li>
<li class="tocline">4.7 <a href="#S4.7" shape="rect">Root
Rule</a></li>
<li class="tocline">4.8 <a href="#S4.8" shape="rect">Tag
Format</a></li>
<li class="tocline">4.9 <a href="#S4.9" shape="rect">Base URI</a>
<ul class="toc">
<li class="tocline">4.9.1 <a href="#S4.9.1" shape="rect">Resolving
Relative URIs</a></li>
</ul>
</li>
<li class="tocline">4.10 <a href="#S4.10" shape=
"rect">Pronunciation Lexicon</a></li>
<li class="tocline">4.11 <a href="#S4.11" shape="rect">Meta
Data</a>
<ul class="toc">
<li class="tocline">4.11.1 <a href="#S4.11.1" shape="rect">Meta and
HTTP-Equiv</a></li>
<li class="tocline">4.11.2 <a href="#S4.11.2" shape="rect">Metadata
(XML Only)</a></li>
</ul>
</li>
<li class="tocline"><span>4.12</span> <a href="#S4.12" shape=
"rect"><span>Tag</span></a></li>
<li class="tocline"><span>4.13</span> <a href="#S4.12" shape=
"rect">Comments</a></li>
<li class="tocline"><span>4.14</span> <a href="#S4.14" shape=
"rect">Grammar Fetching</a></li>
<li class="tocline"><span>4.15</span> <a href="#S4.15" shape=
"rect">ABNF Keywords</a></li>
</ul>
<h3 id="id-S4.1"><a id="S4.1" name="S4.1" shape="rect">4.1 Grammar
Header Declarations</a></h3>
<p>A legal stand-alone grammar header consists of a number of
required declarations and other optional declarations. In addition,
the ABNF Form and XML Form each have additional requirements and
capabilities of the header that are specific to each syntactic
form. The ordering of header declarations is also specific to the
two forms.</p>
<p>The table summarizes the information declared in a grammar
header and the appropriate representation in the ABNF Form and XML
Form.</p>
<table border="1" cellpadding="3" summary=
"Grammar Header Declarations" width="100%">
<tr>
<td colspan="1" rowspan="1"><b>Declaration</b></td>
<td colspan="1" rowspan="1"><b>Status</b></td>
<td colspan="1" rowspan="1"><b>ABNF Form</b></td>
<td colspan="1" rowspan="1"><b>XML Form</b></td>
</tr>
<tr>
<td colspan="1" rowspan="1">Grammar version</td>
<td colspan="1" rowspan="1">Required</td>
<td colspan="1" rowspan="1"><a href="#S4.2" shape=
"rect">&sect;4.2</a>: ABNF self-identifying header</td>
<td colspan="1" rowspan="1"><a href="#S4.3" shape=
"rect">&sect;4.3</a>: <code>version</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">XML Namespace</td>
<td colspan="1" rowspan="1">Required (XML only)</td>
<td colspan="1" rowspan="1">Not applicable</td>
<td colspan="1" rowspan="1"><a href="#S4.3" shape=
"rect">&sect;4.3</a>: <code>xmlns</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Document type</td>
<td colspan="1" rowspan="1">Recommended (XML only)</td>
<td colspan="1" rowspan="1">Not applicable</td>
<td colspan="1" rowspan="1"><a href="#S4.3" shape=
"rect">&sect;4.3</a>: XML DOCTYPE</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Character encoding</td>
<td colspan="1" rowspan="1">Recommended</td>
<td colspan="1" rowspan="1"><a href="#S4.4" shape=
"rect">&sect;4.4</a>: ABNF self-identifying header</td>
<td colspan="1" rowspan="1"><a href="#S4.4" shape=
"rect">&sect;4.4</a>: <code>encoding</code> attribute in XML
declaration</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Language</td>
<td colspan="1" rowspan="1">Required in voice mode<br clear=
"none" />
Ignored in DTMF mode</td>
<td colspan="1" rowspan="1"><a href="#S4.5" shape=
"rect">&sect;4.5</a>: <code>language</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.5" shape=
"rect">&sect;4.5</a>: <code>xml:lang</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Mode</td>
<td colspan="1" rowspan="1">Optional</td>
<td colspan="1" rowspan="1"><a href="#S4.6" shape=
"rect">&sect;4.6</a>: <code>mode</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.6" shape=
"rect">&sect;4.6</a>: <code>mode</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Root rule</td>
<td colspan="1" rowspan="1">Optional</td>
<td colspan="1" rowspan="1"><a href="#S4.7" shape=
"rect">&sect;4.7</a>: <code>root</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.7" shape=
"rect">&sect;4.7</a>: <code>root</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Tag format</td>
<td colspan="1" rowspan="1">Optional</td>
<td colspan="1" rowspan="1"><a href="#S4.8" shape=
"rect">&sect;4.8</a>: <code>tag-format</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.8" shape=
"rect">&sect;4.8</a>: <code>tag-format</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Base URI</td>
<td colspan="1" rowspan="1">Optional</td>
<td colspan="1" rowspan="1"><a href="#S4.9" shape=
"rect">&sect;4.9</a>: <code>base</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.9" shape=
"rect">&sect;4.9</a>: <code>xml:base</code> attribute on
<code>grammar</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Pronunciation lexicon</td>
<td colspan="1" rowspan="1">Optional. Multiple allowed.</td>
<td colspan="1" rowspan="1"><a href="#S4.10" shape=
"rect">&sect;4.10</a>: <code>lexicon</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.10" shape=
"rect">&sect;4.10</a>: <code>lexicon</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Metadata</td>
<td colspan="1" rowspan="1">Optional. Multiple allowed.</td>
<td colspan="1" rowspan="1"><a href="#S4.11.1" shape=
"rect">&sect;4.11.1</a>: <code>meta</code> and
<code>http-equiv</code> declarations</td>
<td colspan="1" rowspan="1"><a href="#S4.11.1" shape=
"rect">&sect;4.11.1</a>: <code>meta</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">XML metadata</td>
<td colspan="1" rowspan="1">Optional. (XML Only)</td>
<td colspan="1" rowspan="1">Not applicable</td>
<td colspan="1" rowspan="1"><a href="#S4.11.2" shape=
"rect">&sect;4.11.2</a>: <code>metadata</code> element</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Tag</td>
<td colspan="1" rowspan="1">Optional. Multiple allowed.</td>
<td colspan="1" rowspan="1"><a href="#S4.12" shape=
"rect">&sect;4.12</a>: <code>tag</code> declaration</td>
<td colspan="1" rowspan="1"><a href="#S4.12" shape=
"rect">&sect;4.12</a>: <code>tag</code> element</td>
</tr>
</table>
<a id="grammar-version" name="grammar-version" shape="rect"></a>
<p>A grammar that complies to this specification must declare the
version to be "1.0".</p>
<p>Note: the grammar version indicates the version of the
specification implemented by the grammar and is not for versioning
of the grammar content. A <a href="#S4.11.1" shape=
"rect"><code>meta</code></a> or <a href="#S4.11.2" shape=
"rect"><code>metadata</code></a> declaration may be used for
content versioning.</p>
<blockquote>
<h4 id="id-S4.1-abnf">ABNF Form: Header Summary</h4>
<p>A legal header for a stand-alone ABNF document consists of a
required <a href="#S4.2" shape="rect">ABNF self-identifying
header</a> including the grammar version and optional <a href=
"#S4.4" shape="rect">character encoding</a> followed by these
declarations in any order:</p>
<ul>
<li><a href="#S4.5" shape="rect">Language</a></li>
<li><a href="#S4.6" shape="rect">Mode</a></li>
<li><a href="#S4.7" shape="rect">Root rule</a></li>
<li><a href="#S4.8" shape="rect">Tag format</a></li>
<li><a href="#S4.9" shape="rect">Base URI</a></li>
<li><a href="#S4.10" shape="rect">Pronunciation lexicon</a> (any
number)</li>
<li><a href="#S4.11" shape="rect">Meta and http-equiv</a> (any
number)</li>
<li><a href="#S4.12" shape="rect">Tag</a> (any number)</li>
</ul>
<p><a href="#S4.13" shape="rect">ABNF comments</a> may appear
between the declarations in the ABNF header after the ABNF
self-identifying header.</p>
<p>The header declarations are followed by the <a href="#S3" shape=
"rect">rule definitions</a> of the grammar.</p>
<p>The following are two examples of ABNF headers. Note that
ordering of the declarations (except the ABNF self-identifying
header) is unimportant.</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

language en;
mode voice;
root $myRule;
tag-format FORMAT-STRING;
base &lt;http://www.example.com/base-file-path&gt;;
lexicon &lt;http://www.example.com/lexicon.file&gt;;
lexicon &lt;http://www.example.com/strange-city-names.file&gt;~&lt;media-type&gt;;
meta "Author" is "Stephanie Williams";
http-equiv "Date" is "Fri, 10 Feb 2002 17:27:21 GMT";
<span>{var x=1};</span>
</pre>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0;

// A French Canadian grammar
language fr-CA;

// It's a speech grammar
mode voice;

// Here's the root rule
root $QuebecCities;
</pre></blockquote>
<blockquote>
<h4 id="id-S4.1-xml">XML Form: Header Summary</h4>
<p>A legal stand-alone XML Form grammar document consists of:</p>
<ol>
<li>Legal <a href="#S4.3" shape="rect">XML Prolog</a></li>
<li>Root grammar element with the following attributes
<ul>
<li><a href="#S4.3" shape="rect">XML namespace</a></li>
<li><a href="#S4.3" shape="rect">XML Schema attributes</a></li>
<li><a href="#S4.3" shape="rect">Version</a></li>
<li><a href="#S4.5" shape="rect">Language</a></li>
<li><a href="#S4.6" shape="rect">Mode</a></li>
<li><a href="#S4.7" shape="rect">Root rule</a></li>
<li><a href="#S4.8" shape="rect">Tag format</a></li>
<li><a href="#S4.9" shape="rect">Base URI</a></li>
</ul>
</li>
<li><code>grammar</code> element containing any number of the
following elements in any order:
<ul>
<li><a href="#S4.10" shape="rect">Pronunciation lexicon</a> (any
number)</li>
<li><a href="#S4.11.1" shape="rect">Meta and HTTP-Equiv</a> (any
number)</li>
<li><a href="#S4.11.2" shape="rect">Metadata</a> (any number)</li>
<li><a href="#S4.12" shape="rect">Tag</a> (any number)</li>
</ul>
</li>
</ol>
<p><a href="#S3" shape="rect">Rule definitions</a> follow the
<code>lexicon</code>, <code>meta</code>, <code>metadata</code> and
<span><code>tag</code></span> declarations.</p>
<p>The following are examples of XML Form grammars headers each
including all declarations permitted on the <code>grammar</code>
element and one with the DOCTYPE declaration.</p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;grammar version="1.0" 
         xml:lang="en"
         mode="voice"
         root="myRule"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:base="http://www.example.com/base-file-path"&gt;
</pre>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar version="1.0"
         xml:lang="fr-CA"
         mode="voice"
         root="QuebecCities"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:base="http://www.example.com/another-base-file-path"&gt;
</pre></blockquote>
<h3 id="id-S4.2"><a id="S4.2" name="S4.2" shape="rect">4.2 ABNF
Self-Identifying Header</a></h3>
<p>The <em>ABNF self-identifying header</em> must be present in any
legal stand-alone ABNF Form grammar document.</p>
<p>The first character of an ABNF document must be the "#" symbol
(x23) unless preceded by an optional XML 1.0 <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#charencoding" shape=
"rect"><em>byte order mark</em></a> <a href="#ref-xml" shape=
"rect">[XML &sect;4.3.3]</a>. The ABNF byte order mark follows the
XML definition and requirements. For example, documents encoded in
UTF-16 must begin with the byte order mark.</p>
<p>The optional byte order mark and required "#" symbol must be
followed immediately by the exact string "ABNF" (x41 x42 x4d x46)
or the appropriate equivalent for the document's encoding (e.g. for
UTF-16 little-endian: x23 x00 x41 x00 x42 x00 x4d x00 x46 x00). If
the byte order mark is absent on a grammar encoded in UTF-16 then
the grammar processor should perform <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-guessing" shape=
"rect">auto-detection of character encoding</a> in a manner
analogous to auto-detection of character encoding in XML <a href=
"#ref-xml" shape="rect">[XML &sect;F]</a>.</p>
<p>Next follows a single space character (x20) and the required
version number which is "<code>1.0</code>" for this specification
(x31 x2e x30).</p>
<p>Next follows an optional <a href="#S4.4" shape="rect">character
encoding</a>. Section 4.4 defines character encodings in more
detail. If present, there must be a single space character (x20)
between the version number and the character encoding.</p>
<p>The self-identifying header is finalized with a semicolon (x3b)
followed immediately by a newline. The semicolon must be the first
character following the version number or the character encoding if
is present.</p>
<p>For the remaining declarations of the ABNF header <a href=
"#term-whitespace" shape="rect">white space</a> is not
significant.</p>
<h3 id="id-S4.3"><a id="S4.3" name="S4.3" shape="rect">4.3 XML Form
Prolog and Root Element</a></h3>
<p>A legal stand-alone XML Form grammar document must have a legal
<a href="http://www.w3.org/TR/2000/REC-xml-20001006#sec-prolog-dtd"
shape="rect">XML Prolog</a> <a href="#ref-xml" shape="rect">[XML
&sect;2.8]</a>.</p>
<p>The XML prolog in an XML Form grammar comprises the XML
declaration and an optional DOCTYPE declaration referencing the
grammar DTD. It is followed by the root <code>grammar</code>
element. The XML prolog may also contain XML comments, processor
instructions and other content permitted by XML in a prolog.</p>
<p>The version number of the XML declaration indicates which
version of XML is being used. The version number of the
<code>grammar</code> element indicates which version of the grammar
specification is being used &mdash; "<code>1.0</code>" for this
specification. The grammar version is a required attribute.</p>
<p>The grammar element must designate the grammar namespace. This
can be achieved by declaring an <code>xmlns</code> attribute or an
attribute with an "xmlns" prefix. See <a href="#ref-xmlns" shape=
"rect">[XMLNS]</a> for details. Note that when the xmlns attribute
is used alone, it sets the default namespace for the element on
which it appears and for any child elements. The namespace for XML
Form grammars is defined as <a href=
"http://www.w3.org/2001/06/grammar" shape=
"rect">http://www.w3.org/2001/06/grammar</a>.</p>
<p>It is recommended that the grammar element also indicate the
location of the grammar schema (see <a href="#AppC" shape=
"rect">Appendix C</a>) via the <code>xsi:schemaLocation</code>
attribute from <a href="#ref-schema1" shape="rect">[SCHEMA1]</a>.
Although such indication is not required, to encourage it this
document provides such indication on all of the examples:</p>
<pre class="xml" xml:space="preserve">
&lt;grammar version="1.0"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"&gt;
  ...
&lt;/grammar&gt;
</pre>
<p>If present, the optional DOCTYPE must reference the standard
DOCTYPE and identifier.</p>
<pre class="xml" xml:space="preserve">
&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;
</pre>
<p>The character encoding is defined on the XML declaration as
defined by the XML specification. See <a href="#S4.4" shape=
"rect">Section 4.4</a> for detail.</p>
<p>The language is defined by the <code>xml:lang</code> attribute
on the <code>grammar</code> element. See <a href="#S4.5" shape=
"rect">Section 4.5</a> for details.</p>
<p>The grammar <code>mode</code> is defined on the
<code>grammar</code> element. See <a href="#S4.6" shape=
"rect">Section 4.6</a> for details.</p>
<p>The <code>root</code> rule is defined on the
<code>grammar</code> element. See <a href="#S4.7" shape=
"rect">Section 4.7</a> for details.</p>
<p>The <code>tag-format</code> is defined on the
<code>grammar</code> element. See <a href="#S4.8" shape=
"rect">Section 4.8</a> for details.</p>
<p>The base URI for the document is defined by the
<code>xml:base</code> attribute on the <code>grammar</code>
element. See <a href="#S4.9" shape="rect">Section 4.9</a> for
details.</p>
<h3 id="id-S4.4"><a id="S4.4" name="S4.4" shape="rect">4.4
Character Encoding</a></h3>
<p>The character encoding declaration indicates the scheme used for
encoding character data in the document. For example, for US
applications it would be common to use US-ASCII, UTF-8 (8-bit
Unicode) or ISO-8859-1. For Japanese grammars, character encodings
such as EUC-JP and UTF-16 (16-bit Unicode) could be used.</p>
<p>Except for the different syntactic representation, the ABNF Form
follows the character encoding handling defined for XML. XML
grammar processors must accept both the UTF-8 and UTF-16 encodings
of ISO/IEC 10646 and may support other character encodings. This
follows from an XML grammar processor being a compliant XML
processor and thus required to support those character encodings.
For consistency, ABNF grammar processor must also accept both the
UTF-8 and UTF-16 encodings of ISO/IEC 10646 and may support other
character encodings.</p>
<p>For both XML Form and ABNF Form grammars the declaration of the
character encoding is optional but strongly recommended. XML
defines behavior for XML processors that receive an XML document
without a character encoding declaration. For consistency an ABNF
grammar processor must follow the same behavior (with adjustments
for the different syntax). (Note the character encoding declaration
is optional only in cases where it is optional for a legal XML
document.)</p>
<blockquote>
<h4 id="id-S4.4-abnf">ABNF Form</h4>
<p>The character encoding declaration is part of the
self-identifying grammar header defined in <a href="#S4.1" shape=
"rect">Section 4.1</a> and is processed in combination with the
byte order mark, if present, using the same procedure as XML 1.0
<a href="#ref-xml" shape="rect">[XML &sect;4.3.3]</a>.</p>
<p>The following are examples of ABNF self-identifying grammar
headers with and without the character encoding declaration.</p>
<p>Note: the ABNF Form syntax does not provide a character
reference syntax for entry of a specific character, for example,
one not directly accessible from available input devices. This
contrasts with <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-references" shape=
"rect">XML 1.0 syntax for character references</a> <a href=
"#ref-xml" shape="rect">[XML &sect;4.1]</a>. For development
requiring character references the XML Form of the specification is
recommended.</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;
</pre>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 EUC-JP;
</pre>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0;
</pre>
<h4 id="id-S4.4-xml">XML Form</h4>
<p>XML declares character encodings as part of the document's XML
declaration on the first line of the document.</p>
<p>The following are examples of XML headers with and without the
character encoding declaration.</p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;
</pre>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="EUC-JP"?&gt;
</pre>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0"?&gt;
</pre></blockquote>
<h3 id="id-S4.5"><a id="S4.5" name="S4.5" shape="rect">4.5
Language</a></h3>
<p>The language declaration of a grammar provides the <a href=
"#term-language" shape="rect">language identifier</a> that
indicates the primary language contained by the document and
optionally indicates a country or other variation. Additionally,
any legal rule expansion may be <a href="#S2.7" shape=
"rect">labeled with a language identifier</a>.</p>
<p>The language declaration is required for all speech recognition
grammars: i.e. all grammars for which the <a href="#S4.6" shape=
"rect"><code>mode</code></a> is "voice". (Note that mode defaults
to voice if there is no explicit mode declaration in ABNF or
<code>mode</code> attribute in XML.)</p>
<p>If an XML Form grammar is incorporated within another XML
document &mdash; for example, as supported by VoiceXML 2.0 &mdash; then the
<code>xml:lang</code> attribute is optional on the
<code>grammar</code> element and the <code>xml:lang</code>
attribute must be inherited from the enclosing document.</p>
<p>In <a href="#AppE" shape="rect">DTMF grammars</a> a language
declaration must be ignored if present.</p>
<p>The conformance definition in <a href="#S5" shape="rect">Section
5</a> defines the behavior of a grammar processor when it
encounters a language variant that it does not support.</p>
<blockquote>
<h4 id="id-S4.5-abnf">ABNF Form</h4>
<p><span>The ABNF header must contain zero or one language
declaration.</span> It consists of the keyword
"<code>language</code>", <a href="#term-whitespace" shape=
"rect">white space</a>, a legal <a href="#term-language" shape=
"rect">language identifier</a>, optional <a href="#term-whitespace"
shape="rect">white space</a> and a terminating semicolon character
(';').</p>
<pre class="abnf" xml:space="preserve">
language en-US;
</pre>
<pre class="abnf" xml:space="preserve">
language fr;
</pre>
<h4 id="id-S4.5-xml">XML Form</h4>
<p>Following the XML 1.0 specification <a href="#ref-xml" shape=
"rect">[XML &sect;2.12]</a> the <a href="#term-language" shape=
"rect">language identifier</a> is indicated by an
<code>xml:lang</code> attribute on the root <code>grammar</code>
element.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en-US" 
         version="1.0"&gt;
</pre>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="fr"
         version="1.0"&gt;
</pre></blockquote>
<h3 id="id-S4.6"><a id="S4.6" name="S4.6" shape="rect">4.6 Grammar
Mode</a></h3>
<p>The mode of a grammar indicates the type of input that the user
agent should be detecting. The default mode is "<code>voice</code>"
for speech recognition grammars. An alternative input mode defined
in <a href="#AppE" shape="rect">Appendix E</a> is
"<code>dtmf</code>" input.</p>
<p>The <code>mode</code> attribute indicates how to interpret the
<a href="#S2.1" shape="rect">tokens</a> contained by the grammar.
Speech tokens are expected to be detected as speech audio that
sounds like the token. Behavior with DTMF input, if supported, is
defined in <a href="#AppE" shape="rect">Appendix E</a>.</p>
<p>It is often the case that a different user agent is used for
detecting DTMF tones than for speech recognition. The same may be
true for other modes defined in future revisions of the
specification.</p>
<p>The specification does not define a mechanism by which a single
grammar can mix modes: that is, a representation for a mixed
"<code>voice</code>" and "<code>dtmf</code>" grammar is not
defined. Moreover, it is illegal for a rule reference in one
grammar to reference any grammar with a different mode.</p>
<p>A user agent may, however, support the simultaneous activation
of more than one grammar including both "<code>voice</code>" and
"<code>dtmf</code>" grammars. This is necessary, for example, for
DTMF-enabled VoiceXML browsers <a href="#ref-vxml2" shape=
"rect">[VXML2]</a>. (Note: parallel activation implies disjunction
at the root level of the grammars rather than mixing of modes
within the structure of the grammars.)</p>
<blockquote>
<h4 id="id-S4.6-abnf">ABNF Form</h4>
<p><span>The ABNF header must contain zero or one mode
declaration.</span> It consists of the keyword "<code>mode</code>",
<a href="#term-whitespace" shape="rect">white space</a>, either
"<code>voice</code>" or "<code>dtmf</code>" optional <a href=
"#term-whitespace" shape="rect">white space</a> and a terminating
semicolon character (';'). If the ABNF header does not declare the
mode then it defaults to <code>voice</code>.</p>
<pre class="abnf" xml:space="preserve">
  mode voice;
</pre>
<pre class="abnf" xml:space="preserve">
  mode dtmf;
</pre>
<h4 id="id-S4.6-xml">XML Form</h4>
<p>The <code>mode</code> declaration is provided as an optional
<code>mode</code> attribute on the root <code>grammar</code>
element. Legal values are <code>"voice"</code> and
<code>"dtmf"</code>. If the mode attribute is omitted then the
value defaults to <code>voice</code>.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar mode="voice"
         version="1.0"
         xml:lang="en-US"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"&gt; 
</pre>
<pre class="xml" xml:space="preserve">
&lt;grammar mode="dtmf" 
         version="1.0"
                  xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"&gt;
</pre></blockquote>
<h3 id="id-S4.7"><a id="S4.7" name="S4.7" shape="rect">4.7 Root
Rule</a></h3>
<p>Both the XML Form and ABNF Form permit the grammar header to
optionally declare a single rule to be the root rule of the
grammar. The rule declared as the root rule must be defined within
the scope of the grammar. The rule declared as the root rule may be
<a href="#S3.2" shape="rect">scoped</a> as either
<code>public</code> or <code>private</code>.</p>
<p>A<span>n</span> <a href="#S2.2" shape=
"rect"><span>implicit</span> rule reference</a> to the root rule of
a grammar is legal. The syntax for <span>implicitly</span>
referencing root rules is defined in <a href="#S2.2" shape=
"rect">Section 2.2</a>. It is an error to reference a grammar
<span>implicitly</span> by its root if that grammar does not
declare a legal root rule.</p>
<p>Although a grammar is not required to declare a root rule it is
good practice to declare the root rule of any grammar.</p>
<blockquote>
<h4 id="id-S4.7-abnf">ABNF Form</h4>
<p><span>The ABNF header must contain zero or one root rule
declaration.</span> It consists of the keyword "<code>root</code>",
<a href="#term-whitespace" shape="rect">white space</a>, the
<a href="#S3.1" shape="rect">legal rulename</a> of a rule defined
within the grammar prefixed by the dollar sign ('$'), optional
<a href="#term-whitespace" shape="rect">white space</a> and a
terminating semicolon character (';'). If the ABNF header does not
declare the root rule then it is not legal to
<span>implicitly</span> reference the grammar by its root.</p>
<pre class="abnf" xml:space="preserve">
root $rulename;
</pre>
<h4 id="id-S4.7-xml">XML Form</h4>
<p>The <code>root</code> rulename declaration is provided as an
optional <code>root</code> attribute on the <code>grammar</code>
element. The <code>root</code> declaration must identify one rule
defined elsewhere within the same grammar. The value of the root
attribute is an XML IDREF (not a URI) and must not include the
number sign ('#').</p>
<pre class="xml" xml:space="preserve">
&lt;grammar root="rulename" ...&gt; 
</pre></blockquote>
<h3 id="id-S4.8"><a id="S4.8" name="S4.8" shape="rect">4.8 Tag
Format</a></h3>
<p>The <code>tag-format</code> declaration is an optional
declaration of a <em>tag-format identifier</em> that indicates the
content type of all <span><a href="#S2.6" shape="rect">rule
tags</a> and <a href="#S4.12" shape="rect">header tags</a></span>
contained within a grammar.</p>
<p>The tag-format identifier is a <a href="#term-uri" shape=
"rect">URI</a>. It is recommended that the tag format identifier
indicate both the content type and a version. Tags typically
contain content for a <a href="#S1.4" shape="rect">semantic
interpretation</a> processor and in such cases the identifier, if
present, should indicate the semantic processor to use.</p>
<p>Tag-format identifier values beginning with the string
"semantics/x.y" (where x and y are digits) are reserved for use by
the <i>W3C Semantic Interpretation for Speech Recognition</i>
specification <a href="#ref-sem" shape="rect">[SEM]</a> or future
versions of the specification.</p>
<p>Grammar processor handling of tags is undefined if the tag
format declaration is omitted.</p>
<blockquote>
<h4 id="id-S4.8-abnf">ABNF Form</h4>
<p><span>The ABNF header must contain zero or one tag format
declaration.</span> It consists of the keyword
"<code>tag-format</code>", <a href="#term-whitespace" shape=
"rect">white space</a>, a tag format identifier (an ABNF <a href=
"#term-uri" shape="rect">URI</a>), optional <a href=
"#term-whitespace" shape="rect">white space</a> and a terminating
semicolon character (';').</p>
<p>Informative example ("semantics/1.0" is <span>a reserved
identifier)</span> :</p>
<pre class="abnf" xml:space="preserve">
tag-format &lt;semantics/1.0&gt;;
</pre>
<h4 id="id-S4.8-xml">XML Form</h4>
<p>The <code>tag-format</code> is an optional attribute of the
<code>grammar</code> element and contains a tag format
identifier.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar tag-format="semantics/1.0" ...&gt; 
</pre></blockquote>
<h3 id="id-S4.9"><a id="S4.9" name="S4.9" shape="rect">4.9 Base
URI</a></h3>
<p>Relative URIs are resolved according to a <em>base URI</em>,
which may come from a variety of sources. The base URI declaration
allows authors to specify a document's base URI explicitly. See
<a href="#S4.9.1" shape="rect">Section 4.9.1</a> for details on the
resolution of relative URIs.</p>
<p>The path information specified by the base URI declaration only
affects URIs in the document where the element appears.</p>
<p>The base URI declaration is permitted but optional in both the
XML Form and the ABNF Form.</p>
<p>Note: the base URI may be declared in a <a href="#S4.11.1"
shape="rect">meta declaration</a> but the explicit base declaration
is recommended for both the ABNF Form and XML Form.</p>
<blockquote>
<h4 id="id-S4.9-abnf">ABNF Form</h4>
<p><span>The ABNF header must contain zero or one base URI
declaration.</span> It consists of the keyword "<code>base</code>",
<a href="#term-whitespace" shape="rect">white space</a>, a legal
<a href="#term-uri" shape="rect">ABNF URI</a>, optional <a href=
"#term-whitespace" shape="rect">white space</a> and a terminating
semicolon character (';').</p>
<pre class="abnf" xml:space="preserve">
base &lt;http://www.example.com/base-file-path&gt;;
</pre>
<pre class="abnf" xml:space="preserve">
base &lt;http://www.example.com/another-base-file-path&gt;;
</pre>
<h4 id="id-S4.9-xml">XML Form</h4>
<p>The base URI declaration follows <a href="#ref-xml-base" shape=
"rect">[XML-BASE]</a> and is indicated by a <code>xml:base</code>
attribute on the root <code>grammar</code> element.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xml:base="http://www.example.com/base-file-path" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         version="1.0"&gt;
</pre>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xml:base="http://www.example.com/another-base-file-path"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         version="1.0"&gt;
</pre></blockquote>
<h4 id="id-S4.9.1-abnf"><a id="S4.9.1" name="S4.9.1" shape=
"rect">4.9.1 Resolving Relative URIs</a></h4>
<p>User agents must calculate the base URI for resolving relative
URIs according to <a href="#ref-rfc2396" shape=
"rect">[RFC2396]</a>. The following describes how RFC 2396 applies
to grammar documents.</p>
<p>User agents must calculate the base URI according to the
following precedences (highest priority to lowest):</p>
<ol>
<li>The base URI is set by the <code>xml:base</code> attribute on
the <code>grammar</code> element or the <code>base</code>
declaration in the ABNF header (see Section 4.9).</li>
<li>The base URI is provided in a <a href="#S4.11.1" shape=
"rect">meta declaration</a>.</li>
<li>The base URI is given by metadata discovered during a protocol
interaction, such as an HTTP header (see <a href="#ref-rfc2616"
shape="rect">[RFC2616]</a>).</li>
<li>By default, the base URI is that of the current document. Not
all grammar documents have a base URI (e.g., a valid grammar
document may appear in an email and may not be designated by a
URI). Such grammar documents are not valid if they contain relative
URIs and rely on a default base URI.</li>
</ol>
<h3 id="id-S4.10"><a id="S4.10" name="S4.10" shape="rect"></a>4.10
Pronunciation Lexicon</h3>
<p>A grammar may optionally reference one or more external
pronunciation lexicon documents. A lexicon document is identified
by a <a href="#term-uri" shape="rect">URI</a> with an optional
<a href="#term-media-type" shape="rect">media type</a>.</p>
<p>The pronunciation information contained within a lexicon
document is used only for tokens defined within the enclosing
grammar.</p>
<p>The W3C Voice Browser Working Group is developing the
Pronunciation Lexicon Markup Language <a href="#ref-lex" shape=
"rect">[LEX]</a>. The specification will address the matching
process between tokens and lexicon entries and the mechanism by
which a speech recognizer handles multiple pronunciations from
internal and grammar-specified lexicons. Pronunciation handling
with proprietary lexicon formats will necessarily be specific to
the speech recognizer.</p>
<p>Pronunciation lexicons are necessarily language-specific.
Pronunciation lookup in a lexicon and pronunciation inference for
any token may use an algorithm that is language-specific. (See
<a href="#S2.1" shape="rect">Section 2.1</a> for additional
information on token handling and pronunciations.)</p>
<blockquote>
<h4 id="id-S4.10-abnf">ABNF Form</h4>
<p>The ABNF header may contain any number of pronunciation lexicon
declarations (zero, one or many). The lexicon declaration consists
of the "<code>lexicon</code>" keyword followed by <a href=
"#term-whitespace" shape="rect">white space</a>, an <a href=
"#term-uri" shape="rect">ABNF URI</a> or <a href="#term-media-type"
shape="rect">ABNF URI with media type</a>, optional white space and
a closing semicolon (';'). (Note that a lexicon URI is not preceded
by a dollar sign as is the case for ABNF rule references.)
Example:</p>
<pre class="abnf" xml:space="preserve">
   #ABNF V1.0 ISO-8859-1;
   language en-US;
   
   lexicon &lt;http://www.example.com/lexicon.file&gt;;
   lexicon &lt;http://www.example.com/strange-city-names.file&gt;~&lt;media-type&gt;;
   ...
</pre>
<h4 id="id-S4.10-xml">XML Form</h4>
<p>Any number of <code>lexicon</code> elements may occur as
immediate children of the <code>grammar</code> element. The
<code>lexicon</code> element must have a <code>uri</code> attribute
specifying a <a href="#term-uri" shape="rect">URI</a> that
identifies the location of the pronunciation lexicon document.</p>
<p>The <code>lexicon</code> element may have a <code>type</code>
attribute that specifies the <a href="#term-media-type" shape=
"rect">media type</a> of the pronunciation lexicon document.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en" version="1.0"&gt;
   
   &lt;lexicon uri="http://www.example.com/lexicon.file"/&gt;
   &lt;lexicon uri="http://www.example.com/strange-city-names.file" type="media-type"/&gt;
   ...
</pre></blockquote>
<h3 id="id-S4.11"><a id="S4.11" name="S4.11" shape="rect">4.11 Meta
Data</a></h3>
<p>Grammar documents let authors specify metadata &mdash; information
about a document rather than document content &mdash; in a number of
ways.</p>
<p>A <a href="#S4.11.1" shape="rect"><code>meta</code>
declaration</a> in either the ABNF Form or XML Form may be used to
express metadata information in both XML Form and ABNF Form
grammars or to reference metadata available in an external
resource. The XML Form also supports a <a href="#S4.11.2" shape=
"rect"><code>metadata</code> element</a> that provides a more
general and powerful treatment of metadata information than
<code>meta</code>. Since <code>metadata</code> requires an XML
metadata schema which cannot be expressed in ABNF, there is no
equivalent of <code>metadata</code> in the ABNF Form of
grammars.</p>
<h4 id="id-S4.11.1"><a id="S4.11.1" name="S4.11.1" shape=
"rect">4.11.1 Meta and HTTP-Equiv</a></h4>
<p>A <code>meta</code> declaration in either ABNF Form or the XML
Form associates a string to declared meta property or declares
"http-equiv" content.</p>
<p>The <code>seeAlso</code> property is the only defined meta
property name. It is used to specify a resource that might provide
additional metadata information about the containing grammar. This
property is modelled on the <a href=
"http://www.w3.org/TR/2000/CR-rdf-schema-20000327/#s2.3.4" shape=
"rect"><code>rdfs:seeAlso</code> property</a> of Resource
Description Framework (RDF) Schema Specification 1.0 <a href=
"#ref-rdf-schema" shape="rect">[RDF-SCHEMA &sect;2.3.4]</a>.</p>
<p>It is recommended that for general metadata properties that
grammar authors follow the metadata properties defined in the
Dublin Core Metadata Initiative <a href="#ref-dc" shape=
"rect">[DC]</a>. For example, "Creator" to identify the entity
primarily responsible for making the content of the grammar, "Date"
to indicate creation date, or "Source" to indicate the resource
From which a grammar is derived (e.g. when converting an XML Form
grammar to the ABNF Form, use "Source" to provide the URI for the
original document.)</p>
<blockquote>
<h4 id="id-S4.11.1-abnf">ABNF Form</h4>
<p>The ABNF header may contain any number of meta declarations and
http-equiv declarations (zero, one or many). Each declaration
consists of the "<code>meta</code>" or "<code>http-equiv</code>"
keyword followed by <a href="#term-whitespace" shape="rect">white
space</a>, the name string delimited by quotes, the keyword
"<code>is</code>", <a href="#term-whitespace" shape="rect">white
space</a>, the content string delimited by quotes, optional white
space and a closing semicolon (';').</p>
<p>The name string and the content string must be delimited by
either a matching pair of double quotes ('"') or a matching pair of
single quotes ("'").</p>
<p>Informative example:</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0;

meta "Creator" is "Stephanie Williams";
meta "seeAlso" is "http://example.com/my-grammar-metadata.xml";

http-equiv "Expires" is '0';
http-equiv "Date" is "Thu, 12 Dec 2000 23:27:21 GMT"; 
</pre>
<h4 id="id-S4.11.1-xml">XML Form</h4>
<p>A metadata property is declared with a <code>meta</code>
element. Either a <code>name</code> or <code>http-equiv</code>
attribute is required. It is illegal to provide both
<code>name</code> and <code>http-equiv</code> attributes. A
<code>content</code> attribute is required. The <code>meta</code>,
<code>metadata</code> and <code>lexicon</code> elements must occur
before all rule elements contained with the root
<code>grammar</code> element. There are no constraints on the
ordering of the <code>meta</code>, <code>metadata</code> and
<code>lexicon</code> elements.</p>
<p>Informative example:</p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0"?&gt; 
&lt;grammar version="1.0" xml:lang="en-US"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xmlns="http://www.w3.org/2001/06/grammar"&gt; 

  &lt;meta name="Creator" content="Stephanie Williams"/&gt; 
  &lt;meta name="seeAlso" content="http://example.com/my-grammar-metadata.xml"/&gt; 

  &lt;meta http-equiv="Expires" content="0"/&gt; 
  &lt;meta http-equiv="Date" content="Thu, 12 Dec 2000 23:27:21 GMT"/&gt; 
  ... 
&lt;/grammar&gt;
</pre></blockquote>
<h4 id="id-S4.11.2"><a id="S4.11.2" name="S4.11.2" shape=
"rect">4.11.2 XML Metadata (XML Only)</a></h4>
<p>The <code>metadata</code> element is container in which
information about the document can be placed using a metadata
schema. Although any metadata schema can be used with
<code>metadata</code>, it is recommended that the Resource
Description Format (RDF) schema <a href="#ref-rdf-schema" shape=
"rect">[RDF-SCHEMA]</a> is used in conjunction with the general
metadata properties defined in the Dublin Core Metadata Initiative
<a href="#ref-dc" shape="rect">[DC]</a>.</p>
<p>RDF is a declarative language and provides a standard way for
using XML to represent metadata in the form of statements about
properties and relationships of items on the Web. Content creators
should refer to W3C metadata Recommendations <a href=
"#ref-rdf-syntax" shape="rect">[RDF-SYNTAX]</a> and <a href=
"#ref-rdf-schema" shape="rect">[RDF-SCHEMA]</a> when deciding which
metadata RDF schema to use in their documents. Content creators
should also refer to the Dublin Core Metadata Initiative <a href=
"#ref-dc" shape="rect">[DC]</a>, which is a set of generally
applicable core metadata properties (e.g., Title, Creator, Subject,
Description, Copyrights, etc.).</p>
<p>This specification only defines an XML representation for this
form of metadata declaration. There is no ABNF equivalent for
<code>metadata</code>. A conversion of an XML Form grammar to the
ABNF Form may extract the XML metadata into a separate document
that is referenced with a "seeAlso" meta declaration in the ABNF
document. Note: an agent that searches XML documents for metadata
represented with RDF would be unable to locate RDF even if it were
represented in ABNF. Thus, support for RDF in ABNF was considered
low utility.</p>
<blockquote>
<h4 id="id-S4.11.2-xml">XML Form</h4>
<p>Document properties declared with <code>metadata</code> element
can use any metadata schema. The <code>metadata</code>,
<code>meta</code>, and <code>lexicon</code> elements must occur
before all rule elements contained with the root
<code>grammar</code> element. There are no constraints on the
ordering of the <code>metadata</code>, <code>meta</code> and
<code>lexicon</code> elements.</p>
<p>Informative: This is an example of how <code>metadata</code> can
be included in an XML grammar document using the Dublin Core
version 1.0 RDF schema <a href="#ref-dc" shape="rect">[DC]</a>
describing general document information such as title, description,
date, and so on:</p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0"?&gt; 
&lt;grammar
    xmlns="http://www.w3.org/2001/06/grammar" version="1.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
    xml:lang="en-US"&gt;
    
  &lt;metadata&gt;
   &lt;rdf:RDF
       xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
       xmlns:rdfs = "http://www.w3.org/TR/1999/PR-rdf-schema-19990303#"
       xmlns:dc = "http://purl.org/metadata/dublin_core#"&gt;

   &lt;!-- Metadata about the grammar document --&gt;
   &lt;rdf:Description about="http://www.example.com/meta.grxml"
       dc:Title="Digit Grammar"
       dc:Description="Digit Grammar in W3C XML Form"
       dc:Publisher="W3C"
       dc:Language="en"
       dc:Date="2002-02-14"
       dc:Rights="Copyright 2002 Jan Smith"
       dc:Format="application/srgs+xml" &gt;                
       &lt;dc:Creator&gt;
          &lt;rdf:Seq ID="CreatorsAlphabeticalBySurname"&gt;
             &lt;rdf:li&gt;Jackie Crystal&lt;/rdf:li&gt;
             &lt;rdf:li&gt;Jan Smith&lt;/rdf:li&gt;
          &lt;/rdf:Seq&gt;
       &lt;/dc:Creator&gt;
   &lt;/rdf:Description&gt;
  &lt;/rdf:RDF&gt;
 &lt;/metadata&gt;

&lt;/grammar&gt;
</pre></blockquote>
<h3 id="id-S4.12"><a id="S4.12" name="S4.12" shape=
"rect"><span>4.12 Tag</span></a></h3>
<p>A grammar may optionally specify one or more <code>tag</code>
declarations in the header. The content of a <code>tag</code> in
the header, just like a <a href="#S2.6" shape="rect">tag in rule
expansions</a>, is an arbitrary string which may be used for
<a href="#S1.4" shape="rect">semantic interpretation</a>.</p>
<blockquote>
<h4 id="id-S4.12-abnf"><span>ABNF Form</span></h4>
<p>The ABNF header may contain any number of tag declarations
(zero, one or many).</p>
<p>The tag declaration consists a string delimited as described in
<a href="#id-S2.6-abnf" shape="rect">S2.6 ABNF Form</a>, followed
by a closing semicolon (';').</p>
<p>The tag content is all text between the opening and closing
delimiters including leading and trailing <a href=
"#term-whitespace" shape="rect">whitespace</a>. The contents of the
tag are not parsed by the grammar processor.</p>
<pre class="abnf" xml:space="preserve">
   #ABNF V1.0 ISO-8859-1;
   language en-US;
   {<a href="#S1.4" shape="rect">TAG-CONTENT-1</a>};
   {!{<a href="#S1.4" shape="rect">TAG-CONTENT-2</a>}!};
   
   $rule = . . .;
   ...
</pre>
<h4 id="id-S4.12-xml"><span>XML Form</span></h4>
<p>Any number of <code>tag</code> elements may occur as immediate
children of the <code>grammar</code> element. The content of
<code>tag</code> is CDATA.</p>
<pre class="xml" xml:space="preserve">
&lt;grammar xmlns="http://www.w3.org/2001/06/grammar" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en" version="1.0"&gt;
   
   &lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>&lt;tag&gt;
   &lt;tag&gt;<a href="#S1.4" shape=
"rect">TAG-CONTENT-2</a>&lt;tag&gt;

   ...
</pre></blockquote>
<h3 id="id-S4.13"><a id="S4.13" name="S4.13" shape=
"rect"><span>4.13</span> Comments</a></h3>
<p>Comments may be placed in most places in a grammar document. For
XML, use XML comments. For ABNF there are documentation comments
and C/C++/Java-style comments.</p>
<blockquote>
<h4 id="id-S4.13-abnf">ABNF Form</h4>
<p>C/C++/Java comments are permitted. Documentation comments are
permitted before <code>grammar</code> and <code>language</code>
declarations and before any <code>rule</code> definition.</p>
<p><a href="#S3.3" shape="rect">Section 3.3</a> defines the format
for representing examples in documentation comments before a rule
definition.</p>
<pre class="abnf" xml:space="preserve">
// C++/Java-style single-line comment
/* C/C++/Java-style comment */
/** Java-style documentation comment */
</pre>
<h4 id="id-S4.13-xml">XML Form</h4>
<p>An XML comment has the following syntax.</p>
<pre class="xml" xml:space="preserve">
&lt;!-- comment --&gt;
</pre></blockquote>
<h3 id="id-S4.14"><a id="S4.14" name="S4.14" shape=
"rect"><span>4.14</span> Grammar Fetching</a></h3>
<p>The fetching and caching behavior of both ABNF Form and XML Form
grammar documents is defined primarily by the environment in which
the grammar processor operates. For instance, VoiceXML 1.0 and
VoiceXML 2.0 define certain fetching and caching behaviors that
apply to grammars activated by a VoiceXML browser. Similarly, any
API for a recognizer that supports ABNF Form or XML Form grammars
may apply fetching and caching behaviors.</p>
<p>Grammar processors are recommended to support the following
interpretation of "rendering" a grammar for the purpose of
determining document freshness.</p>
<p><em>Activation</em> of a grammar is the point at which the
recognizer begins detection of user input matching the grammar and
is therefore analogous to the action of visual or audio rendering
of system output. As with output rendering, grammar freshness
should be checked close to the moment of grammar activation.</p>
<h3 id="id-S4.15"><a id="S4.15" name="S4.15" shape=
"rect"><span>4.15</span> ABNF Keywords</a></h3>
<p>ABNF keywords are case sensitive. The keywords of the ABNF
language are not reserved. The keywords with specified meaning in
ABNF are:</p>
<table border="1" cellpadding="3" summary="ABNF Keywords">
<tr>
<th colspan="1" rowspan="1">Context</th>
<th colspan="1" rowspan="1">Keywords</th>
</tr>
<tr>
<td colspan="1" rowspan="1">Language declaration</td>
<td colspan="1" rowspan="1">"language"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Mode declaration</td>
<td colspan="1" rowspan="1">"mode"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Root declaration</td>
<td colspan="1" rowspan="1">"root"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Tag format declaration</td>
<td colspan="1" rowspan="1">"tag-format"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Base URI declaration</td>
<td colspan="1" rowspan="1">"base"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Pronunciation lexicon</td>
<td colspan="1" rowspan="1">"lexicon"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Meta or HTTP-equiv declaration</td>
<td colspan="1" rowspan="1">"meta", "http-equiv", "is"</td>
</tr>
<tr>
<td colspan="1" rowspan="1">Rule definition</td>
<td colspan="1" rowspan="1">"public", "private"</td>
</tr>
</table>
<p>Since keywords are not reserved they may be used as rulenames
and as tokens. The following is a legal grammar that accepts as
input a sequence of one or more "public" tokens.</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

language en-AU;
root $public;
mode voice;

public $public = public $public | public;
</pre>
<h2 id="id-S5"><a id="S5" name="S5" shape="rect">5.
Conformance</a></h2>
<p><strong>This section is normative.</strong></p>
<p>Different sets of grammar conformance criteria exist for:</p>
<ul>
<li class="tocline">5.1 <a href="#S5.1" shape="rect">Conforming XML
Form Grammar Fragments</a></li>
<li class="tocline">5.2 <a href="#S5.2" shape="rect">Conforming
Stand-Alone XML Form Grammar Document</a></li>
<li class="tocline">5.3 <a href="#S5.3" shape="rect">Using XML Form
Grammars with other Namespaces</a></li>
<li class="tocline">5.4 <a href="#S5.4" shape="rect">Conforming XML
Form Grammar Processors</a></li>
<li class="tocline">5.5 <a href="#S5.5" shape="rect">Conforming
Stand-Alone ABNF Form Grammar Documents</a></li>
<li class="tocline">5.6 <a href="#S5.6" shape="rect">Conforming
ABNF Form Grammar Processors</a></li>
<li class="tocline">5.7 <a href="#S5.7" shape="rect">Conforming
ABNF/XML Form Grammar Processors</a></li>
<li class="tocline">5.8 <a href="#S5.8" shape="rect">Conforming
User Agents</a></li>
</ul>
<h3 id="id-S5.1"><a id="S5.1" name="S5.1" shape="rect">5.1:
Conforming XML Form Grammar Fragments</a></h3>
<p>An XML Form grammar document fragment is a <em>Conforming XML
Form Grammar Fragment</em> if:</p>
<ul>
<li>it is a <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-well-formed" shape=
"rect">well-formed</a> XML document <a href="#ref-xml" shape=
"rect">[XML]</a> conforming to namespaces in XML <a href=
"#ref-xmlns" shape="rect">[XMLNS]</a></li>
<li>and it conforms to the criteria for <a href="#S5.2" shape=
"rect">Conforming Stand-Alone XML Form Grammar Document</a> after:
<ul>
<li>all non-grammar namespace elements and attributes and all
<code>xmlns</code> attributes which refer to non-grammar namespace
elements are removed from the document,</li>
<li>and, an appropriate XML declaration (i.e.,
<code>&lt;?xml...?&gt;</code>) is included at the top of the
document,</li>
<li>and, if the <code>grammar</code> element does not already
designate the grammar namespace using the "xmlns" attribute, then
<code>xmlns="http://www.w3.org/2001/06/grammar"</code> is added to
the element.</li>
</ul>
</li>
</ul>
<h3 id="id-S5.2"><a id="S5.2" name="S5.2" shape="rect">5.2:
Conforming Stand-Alone XML Form Grammar Document</a></h3>
<p>A document is a <em>Conforming Stand-Alone XML Form Grammar
Document</em> if it meets both the following conditions.</p>
<ul>
<li>It is a <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-well-formed" shape=
"rect">well-formed</a> XML document <a href="#ref-xml" shape=
"rect">[XML]</a> conforming to namespaces in XML <a href=
"#ref-xmlns" shape="rect">[XMLNS]</a>.</li>
<li>It is <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-prolog-dtd" shape=
"rect">valid XML document</a> which adheres to the specification
described in this document (<a href="#S1" shape="rect">Speech
Recognition Grammar Specification</a>) including the constraints
expressed in the schema (see <a href="#AppC" shape="rect">Appendix
C</a>) and having an XML Form prolog and &lt;grammar&gt; root
element as specified in <a href="#S4.3" shape="rect">Section
4.3</a> and</li>
</ul>
<p>The XML Form grammar specification and these conformance
criteria provide no designated size limits on any aspect of grammar
documents. There are no maximum values on the number of elements,
the amount of character data, or the number of characters in
attribute values.</p>
<h3 id="id-S5.3"><a id="S5.3" name="S5.3" shape="rect">5.3 Using
XML Form Grammars with other Namespaces</a></h3>
<p>The grammar namespace may be used with other XML namespaces as
per the Namespaces in XML Recommendation <a href="#ref-xmlns"
shape="rect">[XMLNS]</a>. Future work by W3C will address ways to
specify conformance for documents involving multiple
namespaces.</p>
<h3 id="id-S5.4"><a id="S5.4" name="S5.4" shape="rect">5.4
Conforming XML Form Grammar Processors</a></h3>
<p>An XML Form grammar processor is a program that can parse and
process XML Form grammar documents. Examples include speech
recognizers and DTMF detectors that accept the XML Form.</p>
<p>In a <em>Conforming XML Form Grammar Processor</em>, the XML
parser must be able to parse and process all XML constructs defined
by XML 1.0 <a href="#ref-xml" shape="rect">[XML]</a> and Namespaces
in XML <a href="#ref-xmlns" shape="rect">[XMLNS]</a>. This XML
parser is not required to perform validation of a grammar document
as per its schema or DTD; this implies that during processing of an
XML Form grammar document it is optional to apply or expand
external entity references defined in an external DTD.</p>
<p>A Conforming XML Form Grammar Processor must correctly
understand and apply the semantics of each possible grammar feature
defined by this document.</p>
<p>A Conforming XML Form Grammar Processor must meet the following
requirements for handling of languages:</p>
<ul>
<li>A Conforming Grammar Processor is required to parse all legal
language declarations successfully.</li>
<li>A Conforming Grammar Processor should inform its hosting
environment if it encounters a language that it can not
support.</li>
<li>A Conforming Grammar Processor that can support a given
language, must be able to activate the root, any single public
rule, or any set of public rules or roots of one or many grammars
where each rule or root and all directly or indirectly referenced
sub-rules are for this same given language.</li>
<li>A Conforming Grammar Processor may activate a part (i.e., the
root, any single public rule, or any set of public rules) of one or
many grammars where the parts contain multiple languages, with one or
more languages in each part. When a processor is able to support each
language in the set but is unable to handle them concurrently it
should inform the hosting environment. When the set includes one or
more languages that are not supported by the processor it should
inform the hosting environment.</li>
<li>A Conforming Grammar Processor may implement languages by
approximate substitutions according to a documented,
platform-specific behavior. For example, using a US English speech
recognizer to process British English input.</li>
</ul>
<p>When a Conforming XML Form Grammar Processor encounters elements
or attributes in a non-grammar namespace it may:</p>
<ul>
<li>ignore the non-standard elements and/or attributes</li>
<li>or, process the non-standard elements and/or attributes</li>
<li>or, reject the document containing those elements and/or
attributes</li>
</ul>
<p>A Conforming XML Form Grammar Processor is not required to
support recursive grammars, that is, grammars in which <a href=
"#S2.2" shape="rect">rule references</a> include direct or indirect
self-reference.</p>
<p>There is, however, no conformance requirement with respect to
performance characteristics of the XML Form Grammar Processor. For
instance, no statement is required regarding the accuracy, speed or
other characteristics of a speech recognizer or DTMF detector. No
statement is made regarding the size of grammar or size of grammar
vocabulary that an XML Form Grammar Processor must support.</p>
<h3 id="id-S5.5"><a id="S5.5" name="S5.5" shape="rect">5.5:
Conforming Stand-Alone ABNF Form Grammar Documents</a></h3>
<p>An ABNF grammar document is a Conforming ABNF Document if it
adheres to the specification described in this document (<a href=
"#S1" shape="rect">Speech Recognition Grammar Specification</a>)
including the <a href="#AppD" shape="rect">Formal ABNF
Specification</a>.</p>
<h3 id="id-S5.6"><a id="S5.6" name="S5.6" shape="rect">5.6:
Conforming ABNF Form Grammar Processor</a></h3>
<p>An ABNF Grammar Processor is a program that can parse and
process ABNF grammar documents. Examples include speech recognizers
and DTMF detectors that accept the ABNF Form.</p>
<p>A Conforming ABNF Grammar Processor must correctly understand
and apply the semantics of each possible grammar feature defined by
this document.</p>
<p>A Conforming ABNF Grammar Processor must follow the same
language handling requirements as outlined in <a href="#S5.4"
shape="rect">Section 5.4</a> for Conforming XML Form Grammar
Processors.</p>
<p>A Conforming ABNF Grammar Processor should inform its hosting
environment if it encounters an illegal grammar document or other
grammar content that it is unable to process.</p>
<p>A Conforming ABNF Grammar Processor is not required to support
recursive grammars, that is, grammars in which <a href="#S2.2"
shape="rect">rule references</a> include direct or indirect
self-reference.</p>
<p>There is, however, no conformance requirement with respect to
performance characteristics of the ABNF Grammar Processor. For
instance, no statement is required regarding the accuracy, speed or
other characteristics of a speech recognizer or DTMF detector. No
statement is made regarding the size of grammar or size of grammar
vocabulary that an ABNF Grammar Processor must support.</p>
<h3 id="id-S5.7"><a id="S5.7" name="S5.7" shape="rect">5.7:
Conforming ABNF/XML Form Grammar Processor</a></h3>
<p>A Conforming ABNF/XML Form Grammar Processor must meet all the
conformance criteria defined in <a href="#S5.4" shape=
"rect">Section 5.4</a> and in <a href="#S5.6" shape="rect">Section
5.6</a>.</p>
<p>Additionally an ABNF/XML Form Grammar Processor must be able to
resolve and apply <a href="#S2.2" shape="rect">references</a> from
XML Form Grammars to ABNF Form Grammars, and <a href="#S2.2" shape=
"rect">references</a> from ABNF Form Grammars to XML Form
Grammars.</p>
<h3 id="id-S5.8"><a id="S5.8" name="S5.8" shape="rect">5.8:
Conforming User Agent</a></h3>
<p>A conforming user agent is a <a href="#S5.4" shape=
"rect">Conforming XML Form Grammar Processor</a>, <a href="#S5.6"
shape="rect">Conforming ABNF Form Grammar Processor</a> or <a href=
"#S5.7" shape="rect">Conforming ABNF/XML Form Grammar Processor</a>
that is capable of accepting user input of the <a href="#S4.6"
shape="rect"><code>mode</code></a> of a grammar (i.e. speech input
in <code>"voice"</code> mode, DTMF input <code>"dtmf"</code> mode)
and:</p>
<ol>
<li>Is capable of determining when a sequence of user input exactly
matches a grammar,</li>
<li>Is capable of producing an output representation that indicates
how the input matches the grammar.</li>
</ol>
<p>Current speech recognition technology is statistically based.
Since the output is not deterministic and cannot be guaranteed to
be a correct representation of the input there is no conformance
requirement regarding accuracy. A conformance test may, however,
require some examples of correct recognition of speech input to
determine conformance.</p>
<h2 id="id-S6"><a id="S6" name="S6" shape="rect">6.
Acknowledgements</a></h2>
<p>This document was written with the participation of the members
of the W3C Voice Browser Working Group <em>(listed in alphabetical
order)</em>:</p>
<dl>
<dd>Mike Brown, Lucent Bell Labs<br clear="none" />
Dan Burnett, Nuance Communications<br clear="none" />
Emily Candell, Comverse<br clear="none" />
<span>Jerry Carter, Invited Expert</span><br clear="none" />
<span>Debbie Dahl, Invited Expert</span><br clear="none" />
Debajit Ghosh, Nuance Communications<br clear="none" />
Andrew Hunt, <span>ScanSoft</span><br clear="none" />
<span>Stefan Krause, ScanSoft</span><br clear="none" />
Sol Lerner, <span>ScanSoft</span><br clear="none" />
Bruce Lucas, IBM<br clear="none" />
<span>Jens Marschner, ScanSoft</span><br clear="none" />
Scott McGlashan, <span>Hewlett-Packard</span><br clear="none" />
Yves Normandin, Locus Dialogue<br clear="none" />
Brad Porter, Tellme<br clear="none" />
<span>Dave Raggett, W3C/Canon</span><br clear="none" />
David Ramsthaler, Cisco<br clear="none" />
Luc Van Tichelen, ScanSoft<br clear="none" />
Kuansan Wang, Microsoft<br clear="none" />
Laura Werner, BeVocal<br clear="none" /></dd>
</dl>
<h2 id="id-AppA"><a id="AppA" name="AppA" shape="rect">Appendix A:
References</a></h2>
<h3 id="id-AppA.1"><a id="AppA.1" name="AppA.1" shape="rect">A.1:
Normative References</a></h3>

<dl>
<dt><a id="ref-rfc2119" name="ref-rfc2119" shape=" rect">[RFC2119]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc2119.txt">Key words for use in RFCs to Indicate
Requirement Levels</a></cite>,
    S. Bradner.
     IETF RFC 2119. See http://www.ietf.org/rfc/rfc2119.txt</dd>
<dt><a id="ref-rfc2045" name="ref-rfc2045" shape=" rect">[RFC2045]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc2045.txt">Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies</a></cite>,
    N. Freed and N. Borenstein.
    
IETF RFC 2045. November, 1996. See http://www.ietf.org/rfc/rfc2045.txt</dd>

<dt><a id="ref-rfc2046" name="ref-rfc2046" shape=" rect">[RFC2046]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc2046.txt">Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types</a></cite>,
    N. Freed and N. Borenstein.
     IETF RFC 2046.
November 1996. See http://www.ietf.org/rfc/rfc2046.txt</dd>
<dt><a id="ref-rfc2396" name="ref-rfc2396" shape=" rect">[RFC2396]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc2396.txt">Uniform Resource Identifiers (URI): Generic Syntax</a></cite>,
    T. Berners-Lee, R. Fielding, U.C. Irvine, L. Masinter.
     IETF
RFC 2396. 1998. See http://www.ietf.org/rfc/rfc2396.txt</dd>
<dt><a id="ref-schema1" name="ref-schema1" shape=" rect">[SCHEMA1]</a></dt>

<dd><cite><a href="http://www.w3.org/TR/xmlschema-1/">XML Schema Part 1: Structures</a></cite>,
    H. S. Thompson, et al.
    
W3C Recommendation, May 2001. See http://www.w3.org/TR/xmlschema-1/</dd>
<dt><a id="ref-schema2" name="ref-schema2" shape=" rect">[SCHEMA2]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/xmlschema-2/">XML Schema Part 2: Datatypes</a></cite>,
    P.V. Biron, A. Malhotra.
    
W3C Recommendation, May 2001 See http://www.w3.org/TR/xmlschema-2/</dd>
<dt><a id="ref-mimetypes" name="ref-mimetypes" shape=" rect">[TYPES]</a></dt>
<dd><cite><a href="http://www.iana.org/assignments/media-types/index.html">List of media types (MIME types) registered with IANA</a></cite>.
See http://www.iana.org/assignments/media-types/index.html</dd>
<dt><a id="ref-xml" name="ref-xml" shape="rect">[XML]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/2000/REC-xml-20001006">Extensible Markup Language (XML)
1.0 (Second Edition)</a></cite>,
    World Wide Web Consortium.
     W3C Recommendation, 6 October 2000. See
http://www.w3.org/TR/2000/REC-xml-20001006</dd>
<dt><a id="ref-xml-base" name="ref-xml-base" shape=" rect"/>[XML-BASE]</dt>
<dd><cite><a href="http://www.w3.org/TR/2001/REC-xmlbase-20010627/">XML Base</a></cite>,
    J. Marsh, editor.
     W3C Recommendation, June
2001. See http://www.w3.org/TR/2001/REC-xmlbase-20010627/</dd>

<dt><a id="ref-xmlns" name="ref-xmlns" shape=" rect">[XMLNS]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/REC-xml-names/">Namespaces in XML</a></cite>,
    World Wide Web Consortium.
     W3C
Recommendation. See http://www.w3.org/TR/REC-xml-names/</dd>
</dl>
<h3 id="id-AppA.2"><a id="AppA.2" name="AppA.2" shape="rect">A.2:
Informative References</a></h3>
<dl>
<dt><a id="ref-charmod" name="ref-charmod" shape=" rect">[CHARMOD]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/charmod/">Character Model for the World
Wide Web 1.0</a></cite>,
    World Wide Web Consortium. W3C Working Draft, 20 December 2001. See
http://www.w3.org/TR/charmod/</dd>
<dt><a id="ref-dc" class="ref" shape="rect">[DC]</a></dt>
<dd><cite><a href="http://dublincore.org/">Dublin Core Metadata Initiative</a></cite>,
     See http://dublincore.org/.</dd>
<dt><a id="ref-java" name="ref-java" shape="rect">[JAVA]</a></dt>
<dd><cite><a href="http://java.sun.com/docs/books/jls/">The Java Language
Specification (First Edition)</a></cite>,
    James Gosling, Bill Joy, and Guy Steele.
     Addison-Wesley. See http://java.sun.com/docs/books/jls/</dd>

<dt><a id="ref-jsgf" name="ref-jsgf" shape="rect">[JSGF]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/jsgf/">JSpeech Grammar Format</a></cite>,
    Sun Microsystems.
     Sun
Microsystems submission to W3C. See http://www.w3.org/TR/jsgf/</dd>
<dt><a id="ref-html" name="ref-html" shape="rect">[HTML]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/1999/REC-html401-19991224/">HTML 4.01 Specification.</a></cite>,
    World Wide Web Consortium.
    
W3C Recommendation, 24 December 1999. See http://www.w3.org/TR/1999/REC-html401-19991224/</dd>
<dt><a id="ref-hu79" name="ref-hu79" shape="rect">[HU79]</a></dt>

<dd><cite><a href="">Introduction to Automata
Theory, Languages, and Computation</a></cite>,
    J.E. Hopcroft and J.D. Ullman,
    Addison-Wesley, 1979.</dd>
<dt><a id="ref-iso10646" name="ref-iso10646" shape="rect">[ISO/IEC
10646]</a></dt>
<dd><cite><a href="">ISO/IEC 10646-1993 (E). Information technology &mdash; Universal
Multiple-Octet Coded Character Set (UCS) &mdash; Part 1: Architecture
and Basic Multilingual Plane</a></cite>,
    ISO (International Organization for Standardization).
     [Geneva]: International
Organization for Standardization, 1993 (plus amendments AM 1
through AM 7).</dd>
<dt><a id="ref-jel98" name="ref-jel98" shape=" rect">[JEL98]</a></dt>
<dd><cite><a href="">Statistical methods for speech
recognition</a></cite>,
    F. Jelinek.
     MIT Press, 1998. ISBN: 0-262-10066-5.</dd>

<dt><a id="ref-ngram" name="ref-ngram" shape=" rect">[NGRAM]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/ngram-spec/">Stochastic Language Models
(N-Gram) Specification</a></cite>,
    World Wide Web Consortium.
     W3C Working Draft. See http://www.w3.org/TR/ngram-spec/</dd>
<dt><a id="ref-nlsml" name="ref-nlsml" shape=" rect">[NLSML]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/nl-spec/">Natural Language Semantics
Markup Language.</a></cite>,
    World Wide Web Consortium,
     W3C Working Draft, 20 November 2000. See
http://www.w3.org/TR/nl-spec/</dd>
<dt><a id="ref-lex" name="ref-lex" shape="rect">[LEX]</a></dt>

<dd><cite><a href="http://www.w3.org/TR/lexicon-reqs/">Pronunciation Lexicon Markup
Requirements</a></cite>,
    World Wide Web Consortium,
     W3C Working Draft, 12th March 2001. See http://www.w3.org/TR/lexicon-reqs/</dd>
<dt><a id="ref-q24" name="ref-q24" shape="rect">[Q24]</a></dt>
<dd><cite><a href="http://www.itu.int/home/index.html">Multifrequency
push-button signal reception</a></cite>,
    International Telecommunication Union.
     ITU Recommendation approved
1988-11. See http://www.itu.int/home/index.html</dd>
<dt><a id="ref-rab93" name="ref-rab93" shape=" rect">[RAB93]</a></dt>

<dd><cite><a href="">Fundamentals of Speech
Recognition</a></cite>,
    L. Rabiner and B.H. Juang,
     Prentice Hall, 1993. ISBN: 0-13-015157-2.</dd>
<dt><a id="ref-rdf-syntax" class="ref" shape=" rect">[RDF-SYNTAX]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/">Resource Description Framework (RDF) Model and Syntax Specification</a></cite>,
    Ora Lassila and Ralph R. Swick. W3C
Recommendation, 22 February 1999. See http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/</dd>
<dt><a id="ref-rdf-schema" class="ref" shape=" rect">[RDF-SCHEMA]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/2000/CR-rdf-schema-20000327/">Resource Description Framework (RDF) Schema Specification 1.0</a></cite>,
    Dan Brickley and R.V. Guha.
     W3C Candidate
Recommendation, March 2000. See http://www.w3.org/TR/2000/CR-rdf-schema-20000327/</dd>

<dt><a id="ref-rfc1766" name="ref-rfc1766" shape=" rect">[RFC1766]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc1766.txt">Tags for the Identification of Languages</a></cite>,
    H. Alvestrand.
     IETF RFC 1766. See http://www.ietf.org/rfc/rfc1766.txt</dd>
<dt><a id="ref-rfc2616" name="ref-rfc2616" shape=" rect">[RFC2616]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc2616.txt">Hypertext Transfer Protocol &mdash;
HTTP/1.1</a></cite>,
    R. Fielding, et al.
     IETF RFC 2616. 1999. See http://www.ietf.org/rfc/rfc2616.txt</dd>
<dt><a id="ref-rfc2732" name="ref-rfc2732" shape=" rect">[RFC2732]</a></dt>

<dd><cite><a href="http://www.ietf.org/rfc/rfc2732.txt">Format for Literal
IPv6 Addresses in URL's</a></cite>,
    R. Hinden, B. Carpenter, L. Masinter.
     IETF RFC 2732. 1999. See http://www.ietf.org/rfc/rfc2732.txt</dd>
<dt><a id="ref-rfc3066" name="ref-rfc3066" shape=" rect">[RFC3066]</a></dt>
<dd><cite><a href="http://www.ietf.org/rfc/rfc3066.txt">Tags for the Identification of
Languages</a></cite>,
    H. Alvestrand.
     IETF RFC 3066. See http://www.ietf.org/rfc/rfc3066.txt</dd>
<dt><a id="ref-sem" name="ref-sem" shape="rect">[SEM]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/semantic-interpretation/">Semantic Interpretation for
Speech Recognition</a></cite>,
    World Wide Web Consortium,
     W3C Working Draft, 16 November 2001. See

http://www.w3.org/TR/semantic-interpretation/</dd>
<dt><a id="ref-talkml" name="ref-talkml" shape=" rect">[TALKML]</a></dt>
<dd><cite><a href="http://www.w3.org/Voice/TalkML/">Introduction to TalkML</a></cite>,
    Dave Raggett.
     W3C Note. See
http://www.w3.org/Voice/TalkML/</dd>
<dt><a id="ref-unicode" name="ref-unicode" shape=" rect">[Unicode]</a></dt>
<dd><cite>The Unicode Standard, Version 2.0</cite>,
    The Unicode Consortium.
     Reading, Mass.: Addison-Wesley Developers Press,
1996.</dd>

<dt><a id="ref-unicode3" name="ref-unicode3" shape=" rect">[Unicode3]</a></dt>
<dd><cite>The Unicode Standard, Version
3.0</cite>,
    The Unicode Consortium.
     Reading, Mass.: Addison-Wesley Developers Press, 2000.
ISBN 0-201-61633-5.</dd>
<dt><a id="ref-vxml1" name="ref-vxml1" shape=" rect">[VXML1]</a></dt>
<dd><cite><a href="http://www.w3.org/TR/2000/NOTE-voicexml-20000505/">Voice eXtensible Markup Language (VoiceXML)
version 1.0</a></cite>,
    VoiceXML Forum.
     W3C Note, 05 May 2000. See http://www.w3.org/TR/2000/NOTE-voicexml-20000505/</dd>
<dt><a id="ref-vxml2" name="ref-vxml2" shape=" rect">[VXML2]</a></dt>

<dd><cite><a href="http://www.w3.org/TR/2001/WD-voicexml20-20011023/">Voice Extensible Markup Language
(VoiceXML) Version 2.0</a></cite>,
    World Wide Web Consortium.
     W3C Working Draft, 23 October 2001.
See http://www.w3.org/TR/2001/WD-voicexml20-20011023/</dd>
</dl>


<h2 id="id-AppB"><a id="AppB" name="AppB" shape="rect">Appendix B:


DTD for XML Form Grammars</a></h2>
<p><b>This appendix is informative.</b></p>
<p>The grammar DTD is located at <a href="grammar.dtd" shape=
"rect">http://www.w3.org/TR/speech-grammar/grammar.dtd</a></p>
<h2 id="id-AppC"><a id="AppC" name="AppC" shape="rect">Appendix C:
XML Schema Definition For XML Form Grammars</a></h2>
<p><b>This appendix is normative.</b></p>
<p>The grammar schema is located at <a href="grammar.xsd" shape=
"rect">http://www.w3.org/TR/speech-grammar/grammar.xsd</a></p>
<p>Note: the grammar schema includes the <a href=
"#schema-no-namespace" shape="rect">no-namespace core schema</a>
(below).</p>
<p><a id="schema-no-namespace" name="schema-no-namespace" shape=
"rect"></a> The <em>no-namespace core schema</em> for grammars is
located at <a href="grammar-core.xsd" shape=
"rect">http://www.w3.org/TR/speech-grammar/grammar-core.xsd</a>. It
may be used as a basis for specifying XML Form Grammar Fragments
embedded in non-grammar namespace schemas.</p>
<h2 id="id-AppD"><a id="AppD" name="AppD" shape="rect">Appendix D:
Formal Syntax for Augmented BNF Form Grammars</a></h2>
<p><b>This appendix is normative.</b></p>
<p>The notation used here follows the <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#sec-notation" shape=
"rect">EBNF notation</a> (Extended Backus-Naur Form) defined in the
XML 1.0 Recommendation <a href="#ref-xml" shape="rect">[XML
&sect;6]</a>.</p>
<p>The <a href="#term-whitespace" shape="rect">white space handling
of the ABNF Form</a> follows white space and end-of-line handling
of XML (see <a href="#S1.6" shape="rect">Section 1.6</a>).</p>
<p><b>Lexical Grammar for ABNF</b></p>
<p>The lexical grammar defines the lexical tokens of the ABNF
format and has single characters as its terminal symbols. As a
consequence neither <a href="#term-whitespace" shape=
"rect">white space</a> characters nor <a href="#S4.13" shape=
"rect">ABNF comments</a> are allowed in lexical tokens unless
explicitly specified.</p>
<pre class="abnf" xml:space="preserve">
SelfIdentHeader  ::=
    '#ABNF' #x20 VersionNumber (#x20 CharEncoding)? ';'
       <em>[Additional constraints:
          - The semicolon (';') must immediately be followed
            by an <a href="#term-whitespace" shape=
"rect">end-of-line</a>.
       ]</em>

VersionNumber    ::=
    '1.0'
     
CharEncoding     ::=
    Nmtoken

BaseURI          ::=
    ABNF_URI

LanguageCode     ::=
    Nmtoken
        <i>[Additional constraints:
          - The language code must be a valid <a href=
"#term-language" shape="rect">language identifier</a>.
        ]</i>

RuleName         ::=
    '$' ConstrainedName

ConstrainedName  ::=
    Name - (Char* ('.' | ':' | '-') Char*)

TagFormat        ::=
    ABNF_URI

LexiconURI       ::=
    ABNF_URI | ABNF_URI_with_Media_Type

SingleQuotedCharacters ::=
    ''' [^']* '''
     
DoubleQuotedCharacters ::=
    '"' [^"]* '"'
     
QuotedCharacters ::=
    SingleQuotedCharacters | DoubleQuotedCharacters

Weight           ::=
    '/' Number '/'


Repeat           ::=
    [0-9]+ ('-' [0-9]*)?
        <em>[Additional constraints:
          - A number to the right of the hyphen must not be
            greater than the number to the left of the hyphen.
        ]</em>


Probability      ::=
    '/' Number '/'
        <i>[Additional constraints:
          - The float value must be in the range of "0.0"
            to "1.0" (inclusive).
        ]</i>

Number            ::=
    [0-9]+  |  [0-9]+ '.' [0-9]*  |  [0-9]* '.' [0-9]+

ExternalRuleRef  ::=
    '$' ABNF_URI | '$' ABNF_URI_with_Media_Type
        <i>[Additional constraints:
          - The referenced grammar must have the same mode
            ("voice" or "dtmf") as the referencing grammar.
          - If the URI reference contains a fragment
            identifier, the referenced rule must be a
            public rule of another grammar.
          - If the URI reference does not contain a fragment
            identifier, i.e. if it is a<span>n implicit</span> root rule reference,
            then the referenced grammar must declare a root
            rule.
        ]</i>

Token            ::=
    Nmtoken | DoubleQuotedCharacters

LanguageAttachment ::=
    '!' LanguageCode

Tag              ::=
    '{' [^}]* '}'
    | '{!{' (Char* - (Char* '}!}' Char*)) '}!}'

------------------------------------------------------------

<b><a href="#term-uri" shape="rect">ABNF_URI</a>
</b> and <b><a href="#term-media-type" shape=
"rect">ABNF_URI_with_Media_Type</a>
</b> are defined
in <a href="#S1.6" shape="rect">Section 1.6 Terminology</a>.

<b>Name</b> is defined by the XML <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#NT-Name" shape=
"rect">Name</a> production <a href="#ref-xml" shape=
"rect">[XML &sect;2.3]</a>.

<b>Nmtoken</b> is defined by the XML <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#NT-Nmtoken" shape=
"rect">Nmtoken</a> production <a href="#ref-xml" shape=
"rect">[XML &sect;2.3]</a>.

<b>NameChar</b> is defined by the XML <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#NT-NameChar" shape=
"rect">NameChar</a> production <a href="#ref-xml" shape=
"rect">[XML &sect;2.3]</a>.

<b>Char</b> is defined by the XML <a href=
"http://www.w3.org/TR/2000/REC-xml-20001006#NT-Char" shape=
"rect">Char</a> production <a href="#ref-xml" shape=
"rect">[XML &sect;2.2]</a>.
</pre>
<p>Note: As mentioned in <a href="#S2.5" shape="rect">Section
2.5</a> the symbols "*", "+" and "?", which are often used in
regular expression languages, are reserved for future use in ABNF
and must not be used at any place in a grammar where the syntax
currently permits a repeat operator.</p>
<p><b>Syntactic Grammar for ABNF</b></p>
<p>The syntactic grammar has lexical tokens defined by the lexical
grammar as its terminal symbols. Between two lexical tokens any
number of <a href="#term-whitespace" shape="rect">white spaces</a>
or <a href="#S4.13" shape="rect">ABNF comments</a> may appear.</p>
<pre class="abnf" xml:space="preserve">
grammar         ::=
    SelfIdentHeader declaration* ruleDefinition*

declaration     ::=
    baseDecl | languageDecl | modeDecl | rootRuleDecl
    | tagFormatDecl | lexiconDecl | metaDecl <span>| tagDecl</span>

baseDecl     ::=
    'base' BaseURI ';'
        <i>[Additional constraints:
          - A base declaration must not appear more than
            once in grammar.
        ]</i>

languageDecl    ::=
    'language' LanguageCode ';'
        <i>[Additional constraints:
          - A language declaration must not appear more than
            once in grammar.
          - A language declaration is required if the
            grammar mode is "voice".
        ]</i>

modeDecl        ::=
    'mode' 'voice' ';' | 'mode' 'dtmf' ';'
        <i>[Additional constraints:
          - A mode declaration must not appear more than
            once in grammar.
        ]</i>

rootRuleDecl    ::=
    'root' RuleName ';'
        <i>[Additional constraints:
          - A root rule declaration must not appear more
            than once in grammar.
          - The root rule must be a rule that is defined
            within the grammar.
        ]</i>

tagFormatDecl   ::=
    'tag-format' TagFormat ';'
        <i>[Additional constraints:
          - A tag-format declaration must not appear more
            than once in grammar.
        ]</i>

lexiconDecl     ::=
    'lexicon' LexiconURI ';'

metaDecl        ::=
   'http-equiv' QuotedCharacters 'is' QuotedCharacters ';'
   | 'meta' QuotedCharacters 'is' QuotedCharacters ';'

<span>
tagDecl        ::=
   Tag ';'
</span>

ruleDefinition  ::=
    scope? RuleName '=' ruleExpansion ';'
        <i>[Additional constraints:
          - The rule name must be unique within a grammar,
            i.e. no rule must be defined more than once
            within a grammar.
        ]</i>

scope           ::=
    'private' | 'public'

ruleExpansion   ::=
    ruleAlternative ( '|' ruleAlternative )*

ruleAlternative ::=
    Weight? sequenceElement+

sequenceElement ::=
    subexpansion | subexpansion repeatOperator

subexpansion    ::=
    Token LanguageAttachment?
    | ruleRef 
    | Tag
    | '(' ')'
    | '(' ruleExpansion ')' LanguageAttachment?
    | '[' ruleExpansion ']' LanguageAttachment?

ruleRef         ::=
    localRuleRef | ExternalRuleRef | specialRuleRef

localRuleRef    ::=
    RuleName
        <i>[Additional constraints:
          - The referenced rule must be defined within the
            same grammar.
        ]</i>

specialRuleRef  ::=
    '$NULL' | '$VOID' | '$GARBAGE'


repeatOperator  ::=
    '&lt;' Repeat Probability? '&gt;'
</pre>
<h2 id="id-AppE"><a id="AppE" name="AppE" shape="rect">Appendix E:
DTMF Grammars</a></h2>
<p><b>This appendix is normative.</b></p>
<p>This section defines a normative representation of a grammar
consisting of <a href="#term-dtmf" shape="rect">DTMF</a> tokens. A
DTMF grammar can be used by a DTMF detector to determine sequences
of legal and illegal DTMF events. All grammar processors that
support grammars of mode <code>"dtmf"</code> must implement this
Appendix. However, not all grammar processors are required to
support DTMF input.</p>
<p>If the <a href="#S4.6" shape="rect">grammar mode</a> is declared
as "dtmf" then <a href="#S2.1" shape="rect">tokens</a> contained by
the grammar are treated as DTMF tones (rather than the default of
speech tokens).</p>
<p>There are sixteen (16) DTMF tones. Of these twelve (12) are
commonly found on telephone sets as the digits "0" through "9" plus
"*" (star) and "#" (pound). The four DTMF tones not typically
present on telephones are "A", "B", "C", "D".</p>
<p>Each of the DTMF symbols is a legal DTMF token in a DTMF
grammar. As in speech grammars, tokens must be separated by
<a href="#term-whitespace" shape="rect">white space</a> in a DTMF
grammar. A space-separated sequence of DTMF symbols represents a
temporal sequence of DTMF entries.</p>
<p>In the ABNF Form the "*" symbol is reserved so double quotes
must always be used to delimit "*" when defining an ABNF DTMF
grammar. It is recommended that the "#" symbol also be quoted. As
an alternative the tokens "star" and "pound" are acceptable
synonyms.</p>
<p>In any DTMF grammar any <a href="#S4.5" shape="rect">language
declaration</a> in a grammar header is ignored and any <a href=
"#S2.7" shape="rect">language attachments</a> to rule expansions
are ignored.</p>
<p>In all other respects a DTMF grammar is syntactically the same
as a speech grammar. For example, DTMF grammars may use <a href=
"#S2.2" shape="rect">rule references</a>, <a href="#S2.2.3" shape=
"rect">special rules</a>, <a href="#S2.6" shape="rect">tags</a> and
other specification features.</p>
<p>The following is a simple DTMF grammar that accepts a 4-digit
PIN followed by a pound terminator. It also permits the sequence of
"*" followed by "9" (e.g. to receive a help message).</p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

mode dtmf;

$digit = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9;
public $pin = $digit &lt;4&gt; "#" | "*" 9;
</pre>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0"?&gt;

&lt;grammar mode="dtmf" version="1.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xmlns="http://www.w3.org/2001/06/grammar"&gt;

&lt;rule id="digit"&gt;
 &lt;one-of&gt;
   &lt;item&gt; 0 &lt;/item&gt;
   &lt;item&gt; 1 &lt;/item&gt;
   &lt;item&gt; 2 &lt;/item&gt;
   &lt;item&gt; 3 &lt;/item&gt;
   &lt;item&gt; 4 &lt;/item&gt;
   &lt;item&gt; 5 &lt;/item&gt;
   &lt;item&gt; 6 &lt;/item&gt;
   &lt;item&gt; 7 &lt;/item&gt;
   &lt;item&gt; 8 &lt;/item&gt;
   &lt;item&gt; 9 &lt;/item&gt;
 &lt;/one-of&gt;
&lt;/rule&gt;

&lt;rule id="pin" scope="public"&gt;
 &lt;one-of&gt;
   &lt;item&gt;
     &lt;item repeat="4"&gt;&lt;ruleref uri="#digit"/&gt;&lt;/item&gt;
     #
   &lt;/item&gt;
   &lt;item&gt;
     * 9
   &lt;/item&gt;
 &lt;/one-of&gt;
&lt;/rule&gt;

&lt;/grammar&gt;
</pre>
<h2 id="id-AppF"><a id="AppF" name="AppF" shape="rect">Appendix F:
XSLT Style Sheet to Convert XML Form Grammars to ABNF Form</a></h2>
<p><b>This appendix is informative.</b></p>
<p>The transformation provided below is illustrative of the
conversion of an XML Form grammar to the Augmented BNF Form. Known
limitations:</p>
<ul>
<li>Comments are not transformed</li>
<li>There is no treatment of empty token elements (which are
illegal in ABNF)</li>
<li>Preserves filenames (e.g. "grammar.grxml") and media types
('application/srgs+xml') in URIs and media type declarations.</li>
<li>Assumes the quoted content within &lt;meta&gt; attributes uses
double quotes. Does not correctly convert &lt;meta&gt; attributes
containing single quotes.</li>
</ul>
<p>The source for this transformation is located at <a href=
"grammar-transformer.xsl" shape=
"rect">http://www.w3.org/TR/speech-grammar/grammar-transformer.xsl</a>.</p>
<h2 id="id-AppG"><a id="AppG" name="AppG" shape="rect">Appendix G.
Media Types and File Suffix</a></h2>
<p><b>This appendix is informative.</b></p>
<p>The W3C Voice Browser Working Group has applied to IANA to
register a <a href="#term-media-type" shape="rect">media type</a>
each for the ABNF Form and XML Form of this Speech Recognition
Grammar Specification.</p>

<ul>
<li>
<p>The ABNF media type identifies ABNF grammars. The media type
applied for is <code>"application/srgs"</code>.</p>
</li>
<li>
<p>Similarly, the XML Form grammar media type identifies XML
Form grammars. The media type applied for is
<code>"application/srgs+xml"</code>.</p>
</li>
</ul>
<p>The W3C Voice Browser Working Group has adopted the convention
of using the ".gram" filename suffix for ABNF grammar documents and
the ".grxml" filename suffix for XML Form grammar documents.</p>
<h2 id="id-AppH"><a id="AppH" name="AppH" shape="rect">Appendix H.
Logical Parse Structure</a></h2>
<p><b>This appendix is informative.</b></p>
<p>This section defines an informative representation of a parsed
result of speech recognition or other user agent processing. This
representation may be used as the basis for subsequent processing
of user input, in particular, <a href="#S1.4" shape="rect">semantic
interpretation</a>. For instance, the W3C Semantic Interpretation
for Speech Recognition specification <a href="#ref-sem" shape=
"rect">[SEM]</a> is defined around the logical parse structure.</p>
<h3 id="id-AppH.1"><a id="AppH.1" name="AppH.1" shape="rect">H.1
Terminology and Notation</a></h3>
<p>This Appendix adopts the terminology and nomenclature of
<em>Introduction to Automata Theory, Languages, and
Computation</em> <a href="#ref-hu79" shape="rect">[HU79]</a>.</p>
<p>Denote the <em>tokens</em> of the alphabet of all tokens
accepted by a grammar as <b>t1, t2...</b>.</p>
<p>An input or output token sequence is a space separated string of
tokens. The logical parse structure contains <a href="#S2.1" shape=
"rect">white-space-normalized tokens</a>. The tokens in the logical
parse structure are optionally delimited by double quotes so that
<a href="#term-whitespace" shape="rect">white space</a> and others
characters can be parsed unambiguously. e.g. <b>t1,t2,"t3 with
space"</b>. (For consistency, all examples in this Appendix include
double quotes.)</p>
<p>Let <b>&epsilon;</b> (epsilon) or "" denote the unique string of
length 0, also known as the empty string.</p>
<p>Denote the <em>tags</em> of the alphabet of all tags accepted by
a grammar as <b>{tag1}, {tag2}, ...</b>.</p>
<p>Denote a legal expansion as <b>E</b>. (A legal expansion is
defined in <a href="#S2" shape="rect">Section 2</a>.)</p>
<p>The expressive power of a rule expansion is a <em>Regular
Expression</em> (see HU79) and has an equivalent <em>Finite
Automaton</em> (see HU79). [The handling of rule references
requires special treatment: see <a href="#AppH.2" shape=
"rect">Section H.2</a>.] The expressive power of the grammar
specification consists of:</p>
<ul>
<li>Tokens: a finite automaton transition with symbol</li>
<li>Tag: a finite automaton transition on &epsilon;</li>
<li>Sequence: concatenation operation on finite automaton</li>
<li>Alternatives: union operation on finite automaton</li>
<li>Repeats: representable by combinations of concatenation,
closure and union.</li>
</ul>
<p>We formalize the logical parse structure by creating a
<em>Finite Automaton with Output</em> (see HU79). This construct is
also referred to as a <em>Finite State Transducer</em>.</p>
<p>We define the transitions for tokens and tags as producing an
output symbol.</p>
<ul>
<li>Token: transition that accepts token <b>t</b> and produces as
output token <b>t</b>.<br clear="none" />
In the notation of HU79: <b>t/t</b></li>
<li>Tag: transition that accepts &epsilon; (no token) and produces
as output <b>{!{tag}!}</b><br clear="none" />
In the notation of HU79: <b>&epsilon;/{!{tag}!}</b></li>
</ul>
<p>We represent parse output as an ordered array of output
entities: <b>[e1,e2,e3,...]</b>.</p>
<p>An entity <b>e</b> may be a token, a tag or a rule expansion
(see <a href="#AppH.2" shape="rect">H.2</a>).</p>
<p>The empty output array is represented as <b>[&epsilon;]</b> or
simply <b>[]</b>.</p>
<h4 id="AppH.1-special">Special Cases</h4>
<p>A $NULL reference is equivalent to a transition that accepts as
input &epsilon; and produces as output &epsilon;. In the notation
of HU79: <b>&epsilon;/&epsilon;</b>.</p>
<p>A $VOID reference is logically equivalent to a missing
transition. It accepts no input and produces no output.</p>
<p>A $GARBAGE reference is equivalent to a transition that accepts
platform specific input and produces as output &epsilon;.</p>
<h4 id="AppH.1-amb">Ambiguity</h4>
<p>An <em>ambiguity</em> occurs when for a specified sequence of
input tokens matched to a specified rule of a grammar there is more
than one distinct logical parse structure that can be produced.</p>
<p>An <em>ambiguity</em> can occur at points of disjunction
(choice) in a grammar. Disjunction exists with the use of <a href=
"#S2.4" shape="rect">alternatives</a> and <a href="#S2.5" shape=
"rect">repeats</a>.</p>
<p>A grammar processor may preserve any number of ambiguous logical
parse structures to create a set of alternative logical parse
structures for the input. It is legal for a grammar processor to
maintain all possible logical parse structures or to dispose of all
but one of the alternatives. There is no specified behavior for
selection of ambiguities amongst possibilities by a grammar
processors. As a result grammars that contain ambiguity do not
guarantee portability of performance. Developers and grammar tools
should be ambiguity-aware.</p>
<p>This Appendix does not illustrate all forms of ambiguous
expansions but provides examples of some of the form common
forms.</p>
<h4 id="AppH.1-examples">Examples</h4>
<p>Matching a token to a token produces an array of 1 token.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">["t1"]</td>
</tr>
</table>
<p>A $NULL reference is matched by an empty input sequence and
output is an empty array.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$NULL</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
</table>
<p>A tag is matched by an empty input sequence and output is an
array of 1 tag.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">{tag} or {!{tag}!}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">[{!{tag}!}]</td>
</tr>
</table>
<p>Concatenation: An expansion consisting of a token and a tag is
matched by input containing the token and produces as output a
token, tag array.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 {tag1}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag1}!}]</td>
</tr>
</table>
<p>Concatenation: an expansion consisting of a sequence of tokens,
tags and $NULLs is matched by input that consists of the contained
tokens. Output consists of the sequence of tokens and tags with
order preserved. e.g.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 $NULL {tag1} t2 {tag2} t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1 t2 t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t2",{!{tag2}!},"t3"]</td>
</tr>
</table>
<p>Parenthetical structure is not preserved in the result. The
following is the same sequence as the previous example but with
parentheticals added to the expansion definition.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">((t1) $NULL) {tag1} (t2 {tag2} t3)</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1 t2 t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t2",{!{tag2}!},"t3"]</td>
</tr>
</table>
<p>Alternatives: a set of many alternative tokens is matched by
input of a single token and produces as output a single token.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 | t2 |t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t2</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">["t2"]</td>
</tr>
</table>
<p>Alternatives: if any single expansion in a set of alternatives
can be matched by null input then the set of alternatives may be
matched by null input and the output is the output of
null-accepting expansion. ($NULL, {tag} and repeat counts of zero
all permit null input.)</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 | t2 | $NULL</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
</table>
<p>With a different null-accepting expansion:</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 | t2 | {tag}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">[{!{tag}!}]</td>
</tr>
</table>
<p>Alternatives and ambiguity: several examples of ambiguous
expansions with the ambiguity arising from alternatives that accept
the same input but produce different output.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 {tag1} | t1 {tag2} | t2</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag1}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag2}!}]</td>
</tr>
</table>
<p>In this example null input is ambiguous.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">{tag1} | {tag2} | $NULL</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">[{!{tag1}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">[{!{tag2}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 3</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
</table>
<p>The following is not ambiguous because the different paths
through the expansion produce the same output.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 | t1 | t2</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">["t1"]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">["t1"]</td>
</tr>
</table>
<p>Repeats: an optional expansion can be either matched by an empty
token sequence or by any token sequence that matches the expansion
contained within the optional.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 &lt;0-1&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input 1</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input 2</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">["t1"]</td>
</tr>
</table>
<p>Repeats: order is preserved upon multiple expansions.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">(t1 {tag1}) &lt;0-3&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input 1</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input 2</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag1}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input 3</em></td>
<td colspan="1" rowspan="1">t1,t1,t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 3</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t1",{!{tag1}!},"t1",{!{tag1}!}]</td>
</tr>
</table>
<p>Repeats and null input: If the contents of an optional expansion
can be matched by an empty input sequence AND the output of
matching the contained expansion is always an empty array then the
output of matching the optional expansion by an empty sequence is
also an empty array.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$NULL &lt;0-1&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
</table>
<p>Ambiguous repeats: If a repeated or optional expansion can be
matched by an empty input sequence BUT the output of matching the
contained expansion may contain tags then the parse is ambiguous.
It is <em>recommended</em> that the parse be minimal: Output 1 is
preferred.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">{tag} &lt;0-&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">""</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">[]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">[{!{tag}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 3</em></td>
<td colspan="1" rowspan="1">[{!{tag}!},{!{tag}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output N</em></td>
<td colspan="1" rowspan="1">
[{!{tag}!},{!{tag}!},{!{tag}!},...]</td>
</tr>
</table>
<p>A similar ambiguity arises if the repeated expansion contains a
alternative expansion that has a null-accepting expansion.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">(t1 | {tag}) &lt;0-3&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">["t1"]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 3</em></td>
<td colspan="1" rowspan="1">[{!{tag}!},"t1"]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 4</em></td>
<td colspan="1" rowspan="1">["t1",{!{tag}!},{!{tag}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 5</em></td>
<td colspan="1" rowspan="1">[{!{tag}!},"t1",{!{tag}!}]</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 6</em></td>
<td colspan="1" rowspan="1">[{!{tag}!},{!{tag}!},"t1"]</td>
</tr>
</table>
<p>A sequence with two repeat expansion can be ambiguous if the two
repeated expansions can accept the same input but produce different
output.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">(t1 {tag1}) &lt;0-2&gt; (t1 {tag2})
&lt;0-2&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t1,t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 1</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t1",{!{tag1}!},"t1",{!{tag1}!}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 2</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t1",{!{tag1}!},"t1",{!{tag2}!}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 3</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag1}!},"t1",{!{tag2}!},"t1",{!{tag2}!}</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output 4</em></td>
<td colspan="1" rowspan="1">
["t1",{!{tag2}!},"t1",{!{tag2}!},"t1",{!{tag2}!}</td>
</tr>
</table>
<h3 id="id-AppH.2"><a id="AppH.2" name="AppH.2" shape="rect">H.2
Parsing Rule References</a></h3>
<p>A rule reference is a legal rule expansion (see <a href="#S2.2"
shape="rect">Section 2.2</a>).</p>
<p>We denote output obtained by matching the token sequence
<b>"t1,t2,..."</b> against the expansion <b>$rulename</b> as
<b>$rulename[e1,e2,...]</b> where <b>"e1,e2,..."</b> is the entity
sequence obtained by matching that token sequence against the rule
expansion defined for $rulename. Where a rule reference to an
external rule is used the ABNF syntax for the rule reference is
used (without any media type). For example,
<code>$&lt;http://www.example.com/grammar.<span>grxml</span>#rulename"&gt;[e1,e2,...]</code>
or a<span>n implicit</span> root rule reference
<code>$&lt;http://www.example.com/grammar.<span>grxml</span>"&gt;[e1,e2,...]</code>.
For brevity, all the examples below use only local rule
references.</p>
<p>The rulename of the top-level rule should enclose the logical
parse structure.</p>
<p>A distinct structure for matching rule references maintains the
parse tree for the result. This structure may be utilized in the
semantic interpretation process or other computational processes
that derive from the parse output structure.</p>
<p>There is no distinction between <a href="#S2.2.1" shape=
"rect">local rule references</a> (within the same grammar) and
<a href="#S2.2.2" shape="rect">external rule references</a>.</p>
<p>There is no distinction between a root reference and a reference
to a named grammar.</p>
<h4 id="AppH.2.example">Examples</h4>
<p>The following is a simple rule reference example.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t1 t2 t3;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$x</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t2,t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">$x["t1","t2","t3"]</td>
</tr>
</table>
<p>The following is a rule reference in sequence.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t2 t3 t4;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 $x t5</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t2,t3,t4,t5</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">["t1",$x["t2","t3","t4"],"t5"]</td>
</tr>
</table>
<p>The following includes a reference to a rule that outputs a
tag.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t2 {tag};</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">t1 $x t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t2,t3</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">["t1",$x["t2",{!{tag}!}],"t3"]</td>
</tr>
</table>
<p>Multiple references to the same rule are permitted.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t1 {tag1};</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$x $x $x</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t1,t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
[$x["t1",{!{tag1}!}],$x["t1",{!{tag1}!}],$x["t1",{!{tag1}!}]]</td>
</tr>
</table>
<p>Rule references may be repeated.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t1 {tag};</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$x &lt;0-&gt;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t1,t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
[$x["t1",{!{tag1}!}],$x["t1",{!{tag1}!}],$x["t1",{!{tag1}!}]]</td>
</tr>
</table>
<h3 id="id-AppH.3"><a id="AppH.3" name="AppH.3" shape="rect">H.3
Recursion</a></h3>
<p>The Speech Recognition Grammar Specification has the expressive
power of a <em>Context Free Grammar</em>. This arises because the
language permits a rule to directly or indirectly reference itself.
[Note: a <a href="#S5.4" shape="rect">Conforming XML Form Grammar
Processor</a> or <a href="#S5.6" shape="rect">Conforming ABNF Form
Grammar Processor</a> is not required to support recursive
grammars.]</p>
<p>There is no distinct representation for a recursive rule
reference.</p>
<h4 id="AppH.3.examples">Examples</h4>
<p>Simple right recursion. Note: this grammar can be written in a
non-recursive (regular expression) form.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = t1 {last} | t1 $x;</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$x</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t1,t1</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
[$x["t1",$x["t1",$x["t1",{!{last}!}]]]]</td>
</tr>
</table>
<p>Embedded recursion. Note that this matches any sequence of
<em>n</em> t1's followed by <em>n</em> t2's.</p>
<table summary="" border="1" cellpadding="3">
<tr>
<td colspan="1" rowspan="1"><em>Rule</em></td>
<td colspan="1" rowspan="1">$x = {bottom} | (t1 $x t2);</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Expansion</em></td>
<td colspan="1" rowspan="1">$x</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Input</em></td>
<td colspan="1" rowspan="1">t1,t1,t2,t2</td>
</tr>
<tr>
<td colspan="1" rowspan="1"><em>Output</em></td>
<td colspan="1" rowspan="1">
[$x["t1",$x["t1",$x[{!{bottom}!}],"t2"],"t2"]]</td>
</tr>
</table>
<h2 id="id-AppI"><a id="AppI" name="AppI" shape="rect">Appendix I.
Features under Consideration for Future Versions</a></h2>
<p><b>This appendix is informative.</b></p>
<p>The following features are under consideration for versions of
the Speech Recognition Grammar Specification after version 1.0:</p>
<ul>
<li>Optimizations for dynamic grammars: e.g. "static" or "volatile"
keywords on rule definitions.</li>
<li>Dynamic variation of weights on alternatives</li>
<li>Definition of grammar fragments</li>
<li>Specified handling of morphological variants of tokens</li>
<li>Inline definition of token pronunciations</li>
<li>Guidance to recognizers on acoustic models</li>
<li>Support for W3C pronunciation lexicon when it is available</li>
<li>Declaration of semantic return types of rules</li>
<li>Possible distinction of "activable" and "exported" rules
(currently merged as "public")</li>
<li>Multi-modal grammars: e.g. speech and DTMF mixed, speech and
keyboard, speech and pointer...</li>
<li>Conformance criteria for grammar generators</li>
<li>Support for timeout parameters within grammars (e.g.
inter-digit timeout for DTMF)</li>
<li>Support for long DTMF tones &mdash; e.g. accept a tone of 1000ms or
longer</li>
<li>XLink for URI references</li>
</ul>
<h2 id="id-AppJ"><a id="AppJ" name="AppJ" shape="rect">Appendix J:
Example Grammars in ABNF Form and XML Form</a></h2>
<p><b>This appendix is informative.</b></p>
<ul>
<li class="tocline">J.1 <a href="#AppJ.1" shape="rect">Simple
Examples (English)</a></li>
<li class="tocline">J.2 <a href="#AppJ.2" shape=
"rect">Cross-Reference Examples (English)</a></li>
<li class="tocline">J.3 <a href="#AppJ.3" shape="rect">Korean
Examples</a></li>
<li class="tocline">J.4 <a href="#AppJ.4" shape="rect">Chinese
Examples</a></li>
<li class="tocline">J.5 <a href="#AppJ.5" shape="rect">Swedish
Examples</a></li>
</ul>
<h3 id="id-AppJ.1"><a id="AppJ.1" name="AppJ.1" shape="rect">J.1:
Simple Examples (English)</a></h3>
<p>The following shows a simple grammar that supports commands such
as "open a file" and "please move the window". It references a
separately-defined grammar for politeness which is not shown
here.</p>
<blockquote>
<h4 id="AppJ.1-abnf">ABNF Form</h4>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 UTF-8;

language en;
mode voice;
root $basicCmd;

meta "author" is "Stephanie Williams";

/**
 * Basic command.
 * @example please move the window
 * @example open a file
 */

public $basicCmd = 
          $&lt;http://grammar.example.com/politeness.gram#startPolite&gt;
          $command
          $&lt;http://grammar.example.com/politeness.gram#endPolite&gt;;

$command = $action $object;
$action = /10/ open {<a href="#S1.4" shape=
"rect">TAG-CONTENT-1</a>} | /2/ close {<a href="#S1.4" shape=
"rect">TAG-CONTENT-2</a>} 
        | /1/ delete {<a href="#S1.4" shape=
"rect">TAG-CONTENT-3</a>} | /1/ move {<a href="#S1.4" shape=
"rect">TAG-CONTENT-4</a>};
$object = [the | a] (window | file | menu);
</pre>
<h4 id="AppJ.1-xml">XML Form</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar xmlns="http://www.w3.org/2001/06/grammar" xml:lang="en"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         version="1.0" mode="voice" root="basicCmd"&gt;

&lt;meta name="author" content="Stephanie Williams"/&gt;

&lt;rule id="basicCmd" scope="public"&gt;
  &lt;example&gt; please move the window &lt;/example&gt;
  &lt;example&gt; open a file &lt;/example&gt;

  &lt;ruleref uri="http://grammar.example.com/politeness.<span>grxml</span>#startPolite"/&gt;

  &lt;ruleref uri="#command"/&gt;
  &lt;ruleref uri="http://grammar.example.com/politeness.<span>grxml</span>#endPolite"/&gt;

&lt;/rule&gt;

&lt;rule id="command"&gt;
  &lt;ruleref uri="#action"/&gt; &lt;ruleref uri="#object"/&gt;
&lt;/rule&gt;

&lt;rule id="action"&gt;
   &lt;one-of&gt;
      &lt;item weight="10"&gt; open   &lt;tag&gt;<a href="#S1.4"
shape="rect">TAG-CONTENT-1</a>&lt;/tag&gt; &lt;/item&gt;
      &lt;item weight="2"&gt;  close  &lt;tag&gt;<a href="#S1.4"
shape="rect">TAG-CONTENT-2</a>&lt;/tag&gt; &lt;/item&gt;
      &lt;item weight="1"&gt;  delete &lt;tag&gt;<a href="#S1.4"
shape="rect">TAG-CONTENT-3</a>&lt;/tag&gt; &lt;/item&gt;
      &lt;item weight="1"&gt;  move   &lt;tag&gt;<a href="#S1.4"
shape="rect">TAG-CONTENT-4</a>&lt;/tag&gt; &lt;/item&gt;
    &lt;/one-of&gt;
&lt;/rule&gt;

&lt;rule id="object"&gt;
  &lt;item repeat="0-1"&gt;
    &lt;one-of&gt;
      &lt;item&gt; the &lt;/item&gt;
      &lt;item&gt; a &lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/item&gt;

  &lt;one-of&gt;
      &lt;item&gt; window &lt;/item&gt;
      &lt;item&gt; file &lt;/item&gt;
      &lt;item&gt; menu &lt;/item&gt;
  &lt;/one-of&gt;
&lt;/rule&gt;

&lt;/grammar&gt;
</pre></blockquote>
<h3 id="id-AppJ.2"><a id="AppJ.2" name="AppJ.2" shape="rect">J.2:
Cross-Reference Examples (English)</a></h3>
<p>These two grammars illustrate referencing between grammars. The
same grammar is shown in both XML Form and ABNF Form.</p>
<blockquote>
<p><b>ABNF: http://www.example.com/places.gram</b></p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

language en;
mode voice;
root $city_state;

public $city = Boston | Philadelphia | Fargo;

public $state = Florida | North Dakota | New York;

// References to local rules
// Artificial example allows "Boston, Florida!"

public $city_state = $city $state;
</pre>
<p><b>ABNF: http://www.example.com/booking.gram</b></p>
<pre class="abnf" xml:space="preserve">
#ABNF 1.0 ISO-8859-1;

language en;
mode voice;

// Reference by URI syntax
public $flight = I want to fly to
   $&lt;http://www.example.com/places.gram#city&gt;;

// Reference by URI syntax
public $exercise = I want to walk to $&lt;http://www.example.com/places.gram#state&gt;;

// <span>Implicit</span> reference to root rule by URI
public $wet = I want to swim to $&lt;http://www.example.com/places.gram&gt;;
</pre>
<p><b>XML Form Grammar:
http://www.example.com/places.<span>grxml</span></b></p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en" version="1.0" root="city_state" mode="voice"&gt;

   &lt;rule id="city" scope="public"&gt;
     &lt;one-of&gt;
       &lt;item&gt;Boston&lt;/item&gt;
       &lt;item&gt;Philadelphia&lt;/item&gt;
       &lt;item&gt;Fargo&lt;/item&gt;
     &lt;/one-of&gt;
   &lt;/rule&gt;

   &lt;rule id="state" scope="public"&gt;
     &lt;one-of&gt;
       &lt;item&gt;Florida&lt;/item&gt;
       &lt;item&gt;North Dakota&lt;/item&gt;
       &lt;item&gt;New York&lt;/item&gt;
     &lt;/one-of&gt;
   &lt;/rule&gt;

   &lt;!-- Reference by URI to a local rule --&gt;
   &lt;!-- Artificial example allows "Boston, Florida"! --&gt;
   &lt;rule id="city_state" scope="public"&gt;
     &lt;ruleref uri="#city"/&gt; &lt;ruleref uri="#state"/&gt;
   &lt;/rule&gt;
&lt;/grammar&gt;
</pre>
<p><b>XML Form Grammar:
http://www.example.com/booking.<span>grxml</span></b></p>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN"
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="en" version="1.0" mode="voice"&gt;

   &lt;!-- Using URI syntax --&gt;
   &lt;rule id="flight" scope="public"&gt;
     I want to fly to 
     &lt;ruleref uri="http://www.example.com/places.<span>grxml</span>#city"/&gt;
   &lt;/rule&gt;

   &lt;!-- Using URI  syntax --&gt;
   &lt;rule id="exercise" scope="public"&gt;
     I want to walk to &lt;ruleref uri="http://www.example.com/places.<span>grxml</span>#state"/&gt;

   &lt;/rule&gt;

   &lt;!-- <span>Implicit</span> reference to root rule of a grammar by URI  --&gt;
   &lt;rule id="wet" scope="public"&gt;
     I want to swim to &lt;ruleref uri="http://www.example.com/places.<span>grxml</span>"/&gt;

   &lt;/rule&gt;
&lt;/grammar&gt;
</pre></blockquote>
<h3 id="id-AppJ.3"><a id="AppJ.3" name="AppJ.3" shape="rect">J.3:
Korean Examples</a></h3>
<p>The following two grammars are XML Form grammars with Korean
yes/no content. The first represents the Korean symbols as Unicode
characters and has UTF-8 encoding. The second represents the same
Unicode characters using character escaping.</p>
<blockquote>
<h4 id="AppJ.3-abnf">ABNF Form Grammar with Unicode Characters in
UTF-8 Encoding</h4>
<pre class="xml" xml:space="preserve">
#ABNF 1.0 UTF-8;

language ko;
mode voice;
root $yes_no_ko;

/* 
 * Simple Korean yes/no grammar 
 * @example &#50696;
 */

public $yes_no_ko = &#50696; | &#50500;&#45768;&#50724; ;
</pre>
<h4 id="AppJ.3-xml">XML Form Grammar with Unicode Characters in
UTF-8 Encoding</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" 
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar xml:lang="ko" version="1.0" mode="voice"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         root="yes_no_ko"&gt;

  &lt;!-- yes/no grammar --&gt;
  &lt;rule id="yes_no_ko" scope="public"&gt;
    &lt;example&gt;&#50696;&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;&#50696;&lt;/item&gt;
      &lt;item&gt;&#50500;&#45768;&#50724;&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt;
</pre>
<h4 id="AppJ.3-xml-esc">XML Form Grammar with Character Escaping of
Unicode Characters</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" 
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar xml:lang="ko" version="1.0" mode="voice"
         xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         root="main"&gt;

  &lt;!-- yes/no grammar --&gt;
  &lt;rule id="yes_no_ko" scope="public"&gt;
    &lt;example&gt;&amp;#50696;&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;&amp;#50696;&lt;/item&gt;
      &lt;item&gt;&amp;#50500;&amp;#45768;&amp;#50724;&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt;
</pre></blockquote>
<h3 id="id-AppJ.4"><a id="AppJ.4" name="AppJ.4" shape="rect">J.4:
Chinese Examples</a></h3>
<p>The following two grammars are XML Form grammars with Chinese
number content. The first represents the Chinese symbols as Unicode
characters with the UTF-8 encoding. The second represents the same
Unicode characters using character escaping.</p>
<blockquote>
<h4 id="AppJ.4-abnf">ABNF Form Grammar with Unicode Characters in
UTF-8 Encoding</h4>
<pre class="xml" xml:space="preserve">
#ABNF 1.0 UTF-8;

language zh;
mode voice;
root $main;

public $main = $digits1_9;

/*
 * @example &#22235;
 */

private $digits1_9 = &#19968; | &#20108; | &#19977; | &#22235; | &#20116; | &#20845; | &#19971; | &#20843; | &#20061;;
</pre>
<h4 id="AppJ.4-xml">XML Form Grammar with Unicode Characters in
UTF-8 Encoding</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="UTF-8"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" 
          "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar version="1.0" xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="zh" mode="voice" root="main"&gt;

  &lt;rule id="main" scope="public"&gt;
    &lt;ruleref uri="#digits1_9"/&gt;
  &lt;/rule&gt;

  &lt;rule id="digits1_9" scope="private"&gt;
    &lt;example&gt;&#22235;&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;&#19968;&lt;/item&gt;
      &lt;item&gt;&#20108;&lt;/item&gt;
      &lt;item&gt;&#19977;&lt;/item&gt;
      &lt;item&gt;&#22235;&lt;/item&gt;
      &lt;item&gt;&#20116;&lt;/item&gt;
      &lt;item&gt;&#20845;&lt;/item&gt;
      &lt;item&gt;&#19971;&lt;/item&gt;
      &lt;item&gt;&#20843;&lt;/item&gt;
      &lt;item&gt;&#20061;&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt; 
</pre>
<h4 id="AppJ.4-xml-esc">XML Form Grammar with Character Escaping of
Unicode Characters</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" 
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar version="1.0" xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="zh" mode="voice" root="main"&gt;

  &lt;rule id="main" scope="public"&gt;
    &lt;ruleref uri="#digits1_9"/&gt;
  &lt;/rule&gt;

  &lt;rule id="digits1_9" scope="private"&gt;
    &lt;example&gt;&amp;#22235;&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;&amp;#19968;&lt;/item&gt;
      &lt;item&gt;&amp;#20108;&lt;/item&gt;
      &lt;item&gt;&amp;#19977;&lt;/item&gt;
      &lt;item&gt;&amp;#22235;&lt;/item&gt;
      &lt;item&gt;&amp;#20116;&lt;/item&gt;
      &lt;item&gt;&amp;#20845;&lt;/item&gt;
      &lt;item&gt;&amp;#19971;&lt;/item&gt;
      &lt;item&gt;&amp;#20843;&lt;/item&gt;
      &lt;item&gt;&amp;#20061;&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt; 
</pre></blockquote>
<h3 id="id-AppJ.5"><a id="AppJ.5" name="AppJ.5" shape="rect">J.5:
Swedish Examples</a></h3>
<p>This Swedish XML Form grammar provides a comprehensive set of
forms of "yes" and "no". All characters are contained within the
ISO-8859-1 (Latin-1) character set.</p>
<blockquote>
<h4 id="AppJ.5-abnf">XML Form Grammar with ISO-8859-1</h4>
<pre class="xml" xml:space="preserve">
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;

&lt;!DOCTYPE grammar PUBLIC "-//W3C//DTD GRAMMAR 1.0//EN" 
                  "http://www.w3.org/TR/speech-grammar/grammar.dtd"&gt;

&lt;grammar version="1.0" xmlns="http://www.w3.org/2001/06/grammar"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xml:lang="sv" mode="voice" root="main"&gt;

  &lt;rule id="main" scope="public"&gt;
    &lt;example&gt;ja det &auml;r r&auml;tt&lt;/example&gt;
    &lt;example&gt;nej det &auml;r fel&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;
        &lt;ruleref uri="#yes_rule"/&gt;
      &lt;/item&gt;
      &lt;item&gt;
        &lt;ruleref uri="#no_rule"/&gt;
      &lt;/item&gt;
    &lt;/one-of&gt;    
  &lt;/rule&gt;

  &lt;rule id="yes_rule" scope="private"&gt;
    &lt;example&gt;ja det &auml;r r&auml;tt&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;exakt&lt;/item&gt;
      &lt;item&gt;javisst&lt;/item&gt;
      &lt;item&gt;
        ja
        &lt;item repeat="0-1"&gt;
          &lt;ruleref uri="#yes_emphasis"/&gt;
        &lt;/item&gt;
      &lt;/item&gt;
      &lt;item&gt;jepp&lt;/item&gt;
      &lt;item&gt;korrekt&lt;/item&gt;
      &lt;item&gt;okej&lt;/item&gt;
      &lt;item&gt;r&auml;tt&lt;/item&gt;
      &lt;item&gt;si&lt;/item&gt;
      &lt;item&gt;s&auml;kert&lt;/item&gt;
      &lt;item&gt;visst&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;

  &lt;rule id="yes_emphasis" scope="private"&gt;
    &lt;example&gt;det st&auml;mmer&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;det gjorde jag&lt;/item&gt;
      &lt;item&gt;
        &lt;item repeat="0-1"&gt;det&lt;/item&gt;
        st&auml;mmer
      &lt;/item&gt;
      &lt;item&gt;det &auml;r r&auml;tt&lt;/item&gt;
      &lt;item&gt;det &auml;r korrekt&lt;/item&gt;
      &lt;item&gt;det &auml;r riktigt&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;

  &lt;rule id="no_rule" scope="private"&gt;
    &lt;example&gt;nej det &auml;r fel&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;icke&lt;/item&gt;
      &lt;item&gt;fel&lt;/item&gt;
      &lt;item&gt;
        nej
        &lt;item repeat="0-1"&gt;
          &lt;ruleref uri="#no_emphasis"/&gt;
        &lt;/item&gt;
      &lt;/item&gt;
      &lt;item&gt;nix&lt;/item&gt;
      &lt;item&gt;no&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;

  &lt;rule id="no_emphasis" scope="private"&gt;
    &lt;example&gt;det &auml;r fel&lt;/example&gt;
    &lt;one-of&gt;
      &lt;item&gt;det gjorde jag inte&lt;/item&gt;
      &lt;item&gt;
        &lt;item repeat="0-1"&gt;det&lt;/item&gt;
        st&auml;mmer inte
      &lt;/item&gt;
      &lt;item&gt;det &auml;r fel&lt;/item&gt;
      &lt;item&gt;absolut inte&lt;/item&gt;
      &lt;item&gt;inte alls&lt;/item&gt;
    &lt;/one-of&gt;
  &lt;/rule&gt;
&lt;/grammar&gt;
</pre></blockquote>
</div>
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