NOTE-xmlp-reqs-20030728
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html lang="en"><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"><title>XML Protocol (XMLP) Requirements</title><style type="text/css">
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</style><link type="text/css" rel="stylesheet" href="http://www.w3.org/StyleSheets/TR/W3C-WG-NOTE.css"></head><body>
<div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" alt="W3C" src="http://www.w3.org/Icons/w3c_home"></a></p>
<h1>XML Protocol (XMLP) Requirements</h1>
<h2>W3C Working Group Note 28 July 2003</h2><dl><dt>This version:</dt><dd>
<a href="http://www.w3.org/TR/2003/NOTE-xmlp-reqs-20030728">http://www.w3.org/TR/2003/NOTE-xmlp-reqs-20030728</a>
</dd><dt>Latest version:</dt><dd>
<a href="http://www.w3.org/TR/xmlp-reqs">http://www.w3.org/TR/xmlp-reqs</a>
</dd><dt>Previous versions:</dt><dd>
<a href="http://www.w3.org/TR/2002/WD-xmlp-reqs-20020626">http://www.w3.org/TR/2002/WD-xmlp-reqs-20020626</a>
</dd><dt>Editors:</dt>
<dd>Vidur Apparao, Netscape</dd>
<dd>Alex Ceponkus, Bowstreet</dd>
<dd>Paul Cotton, Microsoft</dd>
<dd>David Ezell, Hewlett Packard</dd>
<dd>David Fallside, IBM</dd>
<dd>Martin Gudgin, DevelopMentor</dd>
<dd>Oisin Hurley, IONA Technologies</dd>
<dd>John Ibbotson, IBM</dd>
<dd>R. Alexander Milowski, Lexica, LLC</dd>
<dd>Kevin Mitchell, XMLSolutions</dd>
<dd>Jean-Jacques Moreau, Canon</dd>
<dd>Eric Newcomer, IONA Technologies</dd>
<dd>Henrik Frystyk Nielsen, Microsoft</dd>
<dd>Bob Lojek, Intalio</dd>
<dd>Mark Nottingham, Akamai Technologies</dd>
<dd>Waqar Sadiq, Vitria Technology Inc.</dd>
<dd>Stuart Williams, Hewlett Packard</dd>
<dd>Amr Yassin, Philips Research</dd>
</dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> ©2003 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup>(<a href="http://www.lcs.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.org/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>, <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-software">software licensing</a> rules apply.</p></div><hr><div>
<h2><a name="abstract">Abstract</a></h2>
<p>This document describes the XML Protocol Working Group's requirements
for the XML Protocol (XMLP) specification.</p>
</div><div>
<h2><a name="status">Status of this Document</a></h2>
<p>
<em>This section describes the status of this document at the time
of its publication. Other documents may supersede this document. The latest
status of this document series is maintained at the W3C.</em>
</p>
<p>
The XML Protocol Working Group (WG) has decided to discontinue work on the XML Protocol Requirements, and on this document.
The WG developed the XML Protocol Requirements as a guide for evaluating candidate protocols and
for reasoning about the development of the protocol itself. The WG believes the XML Protocol
Requirement document has well served its purpose in this regard, and it no longer intends to do
any further work on it.</p>
<p>
The changes since last revision are links update for the Working Group Charter, the link to the IPR
declaration and the publication as a Working Group Note per
<a href="http://www.w3.org/2003/06/Process-20030618/process.html#tr-end">W3C Process Document, Section 7.5</a>.</p>
<p>Discussion of this document takes place on the public <<a href="mailto:xml-dist-app@w3.org">xml-dist-app@w3.org</a>> mailing list (Archives
<a href="#xml-dist-app">[4]</a>) per the
<a href="http://www.w3.org/2002/10/XML-Protocol-Charter#email">email
communication rules</a> in the XML Protocol Working Group Charter
<a href="#xmlp-charter">[3]</a>.</p>
<p>Patent disclosures relevant to this specification may be found on the Working Group's <a href="http://www.w3.org/2000/xp/Group/2/10/16-IPR-statements.html">patent disclosure page</a>.</p>
<p>This Note has been endorsed by the W3C XML Protocol Working Group, but has not
been reviewed or endorsed by W3C Members.</p>
<p>The XML Protocol Working Group is part of the <a href="http://www.w3.org/2002/ws/Activity">Web Services Activity</a>.</p>
<p>A <a href="http://www.w3.org/TR/">list of all W3C technical reports</a> can be found
at http://www.w3.org/TR/.</p>
</div>
<hr><div class="toc">
<h2><a name="shortcontents">Short Table of Contents</a></h2><p class="toc">1. <a href="#N345">Notations</a><br>2. <a href="#N800">Relationship to WG Charter</a><br>3. <a href="#N396">Requirements on Requirements</a><br>4. <a href="#N435">Requirements</a><br>5. <a href="#N2100">Requirements from other W3C WGs</a><br>6. <a href="#N2690">Usage Scenarios</a><br>7. <a href="#N2678">References</a><br>A. <a href="#N2672">Acknowledgments</a> (Non-Normative)<br></p></div><hr><div class="toc">
<h2><a name="contents">Table of Contents</a></h2><p class="toc">1. <a href="#N345">Notations</a><br>2. <a href="#N800">Relationship to WG Charter</a><br>3. <a href="#N396">Requirements on Requirements</a><br>4. <a href="#N435">Requirements</a><br> 4.1 <a href="#N443">General Requirements</a><br> 4.2 <a href="#N673">Simplicity and Stability</a><br> 4.2.1 <a href="#N674">The XMLP Specification Documents</a><br> 4.2.2 <a href="#N675">The XMLP Technologies</a><br> 4.3 <a href="#N774">Data Encapsulation and Evolvability</a><br> 4.4 <a href="#N1136">Intermediaries</a><br> 4.4.1 <a href="#N1137">Transport Intermediaries</a><br> 4.4.2 <a href="#N1138">Processing Intermediaries</a><br> 4.5 <a href="#N400">Data Representation</a><br> 4.6 <a href="#N1423">Protocol Bindings</a><br> 4.7 <a href="#N1595">Convention for RPC</a><br>5. <a href="#N2100">Requirements from other W3C WGs</a><br> 5.1 <a href="#N2200">XForms Requirements</a><br> 5.2 <a href="#N1573">P3P Requirements</a><br> 5.3 <a href="#L5908">RDF and UML Requirements</a><br>6. <a href="#N2690">Usage Scenarios</a><br>7. <a href="#N2678">References</a><br></p>
<h3><a id="appendix" name="appendix">Appendix</a></h3><p class="toc">A. <a href="#N2672">Acknowledgments</a> (Non-Normative)<br></p></div><hr><div class="body">
<div class="div1">
<h2><a name="N345"></a>1. Notations</h2>
<p>The following terminology and typographical conventions have been used
in this document.</p>
<p>Each requirement and scenario has a three digit number with a prefix
indicating the status as follows:</p>
<ul>
<li>
<p>A "<b>DR</b>nnn" notation indicates a requirement that the
WG is actively considering (<em>has not</em> reached <em>rough</em>
consensus within the WG)</p>
</li>
<li>
<p>An "<b>R</b>nnn" notation indicates a requirement that the
WG is not actively considering at present (<em>has</em> reached
<em>rough</em> consensus within the WG)</p>
</li>
<li>
<p>A "<b>DS</b>nnn" notation indicates a usage scenario that
the WG is actively considering (<em>has not</em> reached <em>rough</em>
consensus within the WG)</p>
</li>
<li>
<p>An "<b>S</b>nnn" notation indicates a usage scenario that
the WG is not actively considering at present (<em>has rough</em> consensus
within the WG)</p>
</li>
</ul>
<p>The numbers used to identify requirements are arbitrary and does not
imply any ordering or significance.</p>
<p>The document includes several verbatim quotes from the XML Protocol WG
Charter <a href="#xmlp-charter">[3]</a> which provide context for the
requirements. The quoted text is <em>emphasized</em> and prefixed with
<b>Charter</b>.</p>
</div>
<div class="div1">
<h2><a name="N800"></a>2. Relationship to WG Charter</h2>
<p>The XML Protocol WG Charter <a href="#xmlp-charter">[3]</a> has two
sections describing what is
<a href="http://www.w3.org/2002/10/XML-Protocol-Charter#scope">in-scope</a>
and what is
<a href="http://www.w3.org/2002/10/XML-Protocol-Charter#outofscope">out-of-scope</a>
of the problem space defined for the WG. The WG considers all the requirements
in <a href="#N435"><b>4. Requirements</b></a> to be in-scope per the Charter.</p>
<p>Reviewers and readers should be familiar with the XML Protocol WG
Charter <a href="#xmlp-charter">[3]</a> because it provides the critical context
for the requirements and any discussion of them.</p>
</div>
<div class="div1">
<h2><a name="N396"></a>3. Requirements on Requirements</h2>
<dl>
<dt class="label"><a name="z900"></a>R900</dt>
<dd>
<p>The XMLP requirements must include usage scenarios that describe
how XMLP is used in various environments (see <a href="#N2690"><b>6. Usage Scenarios</b></a>). The set
of usage scenarios must represent the expected range of XMLP's use. The
scenarios must be used as design cases during the development of XML Protocol,
and it must be possible to determine whether or not the XML Protocol design
enables each scenario. In addition, the usage scenarios are intended to help a
technically competent person understand the role of XMLP.</p>
</dd>
</dl>
</div>
<div class="div1">
<h2><a name="N435"></a>4. Requirements</h2>
<div class="div2">
<h3><a name="N443"></a>4.1 General Requirements</h3>
<p>
<em>
<b>Charter:</b>
"The envelope and the serialization mechanisms
developed by the Working Group may not preclude any programming model nor
assume any particular mode of communication between peers."
</em>
</p>
<dl>
<dt class="label"><a name="z500"></a>R500</dt>
<dd>
<p>The specification will make reasonable efforts to support (but
not define) a broad range of programming models suitable for the applications
intended for XMLP.</p>
</dd>
<dt class="label"><a name="z501"></a>R501</dt>
<dd>
<p>The specification will make reasonable efforts to support (but
not define) a broad range of protocol bindings between communicating peers (see
also section <a href="#N1423"><b>4.6 Protocol Bindings</b></a>).</p>
</dd>
<dt class="label"><a name="z502"></a>R502</dt>
<dd>
<p>The specification developed by the Working Group must support
either directly or via well defined extension mechanisms different messaging
patterns and scenarios. The specification will directly support One-way and
Request-response patterns as part of permanently and intermittently connected
scenarios. The specification will not preclude the development of other
patterns at either the application or transport layers. Examples of such
patterns may include publish-subscribe or multicast delivery. All patterns and
scenarios will be described by relevant usage scenarios (see
<a href="#N2690"><b>6. Usage Scenarios</b></a>).</p>
</dd>
<dt class="label"><a name="z503"></a>R503</dt>
<dd>
<p>The Working Group will coordinate with the
<a href="http://www.w3.org/XML/Activity">W3C XML Activity</a> through the
<a href="http://www.w3.org/XML/Group/">XML Coordination Group</a> (W3C members only) and
shall use available XML technologies whenever possible. If there are cases
where this is not possible, the reasons must be documented thoroughly.</p>
</dd>
<dt class="label"><a name="z504"></a>R504</dt>
<dd>
<p>The specification developed by the XML Protocol Working Group
WG <a href="#xmlp-wg">[2]</a> shall be as lightweight as possible keeping parts
that are mandatory to the minimum. Optional parts of the specification should
be orthogonal to each other allowing non-conflicting configurations to be
implemented.</p>
</dd>
<dt class="label"><a name="z505"></a>R505</dt>
<dd>
<p>The specification must be suitable for use between
communicating parties that do <em>not</em> have <em>a priori
</em>knowledge of each other.</p>
</dd>
<dt class="label"><a name="z506"></a>R506</dt>
<dd>
<p>The specification must focus on the encapsulation and
representation of data being transferred between parties capable of generating
and/or accepting an XMLP envelope.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="N673"></a>4.2 Simplicity and Stability</h3>
<p>
<em>
<b>Charter:</b>
"Focus must be put on simplicity and modularity and
must support the kind of extensibility actually seen on the Web. In particular,
it must support distributed extensibility where the communicating parties do
not have a priori knowledge of each other."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"Simplicity is a key element in making distributed
systems easy to understand, implement, maintain, and evolve. Modularity and
layering are two important design principles for achieving simplicity. Although
simplicity can only be measured in relative terms, the Working Group must
ensure that the complexity of any solution produced is comparable to that of
other current and widespread Web solutions."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"Another important aspect of simplicity is ease of
deployment. The Working Group will look at various ways of deploying XML
Protocol in a manner that is compatible with the existing Web
infrastructure."
</em>
</p>
<p>Over the years, many different companies and individuals have proven
the ability to design and implement workable open protocols for distributed
computing that operate largely within organizational boundaries. The design
center for XMLP must include the interoperation of systems across
organizational boundaries. The aim is to exploit Web philosophy and Web design
principles in order to help foster widespread decentralized computing on the
Web.</p>
<dl>
<dt class="label"><a name="z307"></a>R307</dt>
<dd>
<p>XMLP must be suitable for widespread use across organizational
boundaries in support of the application usage scenarios supplied elsewhere in
this document (see <a href="#N2690"><b>6. Usage Scenarios</b></a>). This suitability requirement
implies simplicity in the language of the XMLP specification, which itself
describes a technology that is simple to understand and to implement correctly
(see also <b>[<a href="#z301">R301</a>]</b>, <b>[<a href="#z301">R301</a>]</b>). Although simplicity
can only be measured in relative terms, the Working Group should ensure that
the complexity of any solution produced is comparable to that of other current
and widespread Web solutions.</p>
</dd>
<dt class="label"><a name="z308"></a>R308</dt>
<dd>
<p>Since XMLP is intended to be a foundation protocol, its
definition should remain simple and stable over time. Explicit use of
modularity and layering in the resulting design will help assure longevity.
Such a framework will allow subsequent extension of the design while leaving
the foundation of the design intact. (<b>[<a href="#z300">R300 (absorbs old DRs: DR023, DR053,
DR088)</a>]</b> and
<b>[<a href="#z302">R302 (Absorbs old DR's: DR107)</a>]</b> relate to stability).</p>
</dd>
</dl>
<p>Requirements for simplicity and stability arise in the context of
the specification documents and in the context of the protocol technologies
being defined.</p>
<p>Simplicity in XMLP implies that many potentially important features
are out of scope for XMLP proper. However, the XML Protocol Working Group
recognizes that providing consistent ways to support these out of scope
features will help keep XMLP stable.</p>
<p>Examples of such features are:</p>
<ol>
<li>
<p>message authentication and encryption (perhaps using SMIME, SSL,
or digital signatures), </p>
</li>
<li>
<p>sessions and transactions (possibly by providing globally unique
identifiers for messages), and </p>
</li>
<li>
<p>service definition and discovery. </p>
</li>
</ol>
<p>Facilities to support features like these may resemble SOAP/1.1
<a href="#soap11">[7]</a> facilities such as the "Header" element.</p>
<div class="div3">
<h4><a name="N674"></a>4.2.1 The XMLP Specification Documents</h4>
<dl>
<dt class="label"><a name="z300"></a>R300 (absorbs old DRs: DR023, DR053,
DR088)</dt>
<dd>
<p>The requirements that XMLP support the use of layering and
be modular, extensible, and transport independent imply that there is an
architectural design model behind XMLP. This architecture and the extensibility
framework must be explicitly defined (<b>[<a href="#z308">R308</a>]</b> references
modularity, <b>[<a href="#z302">R302 (Absorbs old DR's: DR107)</a>]</b> and <b>[<a href="#z700a">R700a Requirement for Extensibility</a>]</b> reference
extensibility, <b>[<a href="#z502">R502</a>]</b> and <b>[<a href="#z600">R600</a>]</b> reference
transport neutrality).</p>
<p> In this context, layering refers to both XMLP's support of
XMLP modules (the layer(s) "above") as well as the capability of XMLP to define
services required (the layer(s) "below") for implementation across a variety of
underlying protocols</p>
</dd>
<dt class="label"><a name="z301"></a>R301</dt>
<dd>
<p>The XMLP specifications should be clear and easy to
understand. This clarity implies that considerable editorial effort will be
required in the structuring of the narrative through both outline/overview and
normative reference material.</p>
</dd>
<dt class="label"><a name="z301a"></a>R301a</dt>
<dd>
<p>The XMLP specification must clearly identify conformance
requirements in a way that enables the conformance of an implementation of the
specification to be tested (see also <a href="#w3c-conformance">[12]</a>).</p>
</dd>
</dl>
</div>
<div class="div3">
<h4><a name="N675"></a>4.2.2 The XMLP Technologies</h4>
<dl>
<dt class="label"><a name="z302"></a>R302 (Absorbs old DR's: DR107)</dt>
<dd>
<p>XMLP must support extensibility of vocabulary between
communicating parties in a way that allows for decentralized extensibility
without prior agreement. The WG must demonstrate through usage scenarios that
the solution supports decentralized extensibility in a modular and layered
manner (see <a href="#N2690"><b>6. Usage Scenarios</b></a>).</p>
<p> To date the web has been enormously successful because it
has enabled the creators of web services adapt the user interfaces they provide
to human users of the web. A goal of XMLP is to achieve similar levels of
evolvability, extensibility and adaptability for interfaces between web
services.</p>
</dd>
</dl>
<dl>
<dt class="label"><a name="z304"></a>R304</dt>
<dd>
<p>XMLP should facilitate the creation of simple applications.
Simple applications are often characterized by message exchange patterns such
as one-way (or event), and two-way (or synchronous) request response
interactions. The specification should make such simple exchange applications
as easy as possible to create and to use.</p>
</dd>
<dt class="label"><a name="z306"></a>R306 (Absorbs old DRs: DR090)</dt>
<dd>
<p>XMLP and applications of XMLP must be easy to
deploy—especially in systems already supporting XML technologies like XML
namespaces <a href="#XMLNS">[10]</a> and XML schemas <a href="#XMLSchemaP1">[8]</a>
<a href="#XMLSchemaP2">[9]</a>.</p>
<p> The ease with which XMLP applications can be deployed will
be crucial to the success of XMLP. The design of the protocol architecture must
be sensitive to the issues arising in the full spectrum of deployment
environments ranging from resource constrained embedded devices (appliances)
through high performance service engines.</p>
</dd>
<dt class="label"><a name="z309"></a>R309</dt>
<dd>
<p>The specification should make reasonable efforts to support
applications that operate on resource constrained devices. Even though any
practical device is resource constrained in any number of dimensions including
but not limited to bandwidth, computational power and storage, the term
"resource constrained device" often refers to hand-portable devices. This
document does not attempt to define the term "resource constrained" nor what
the constraints are for the available resources.</p>
</dd>
</dl>
</div>
</div>
<div class="div2">
<h3><a name="N774"></a>4.3 Data Encapsulation and Evolvability</h3>
<p>
<em>
<b>Charter:</b>
"For two peers to communicate in a distributed
environment, they must first agree on a unit of communication. The XML Protocol
Working Group must define such a unit by defining an encapsulation language
that allows for applications to independently introduce extensions and new
features. In this context, the following requirements for extensions and
features must be met:"
</em>
</p>
<ul>
<li>
<p>
<em>
"They are or can be orthogonal to other
extensions."
</em>
</p>
</li>
<li>
<p>
<em>
"They can be deployed automatically and dynamically across
the Web with no prior coordination and no central authority."
</em>
</p>
</li>
<li>
<p>
<em>
"The sender can require that the recipient either obeys
the semantics defined by an extension or aborts the processing of the
message."
</em>
</p>
</li>
</ul>
<dl>
<dt class="label"><a name="z701a"></a>R701a Requirement for Encapsulation</dt>
<dd>
<p>The XMLP specification must define the concept of an envelope
or outermost syntactical construct or structure within which all other
syntactical elements of the message must be enclosed. The envelope must be
described with XML Schema <a href="#XMLSchemaP1">[8]</a>
<a href="#XMLSchemaP2">[9]</a>.</p>
</dd>
<dt class="label"><a name="z701b"></a>R701b Requirement for Encapsulation</dt>
<dd>
<p>The XMLP specification must also define a processing model
that defines what it means to properly process an XMLP envelope or produce a
fault. This processing model must be independent of any extensions carried
within the envelope. The processing model must apply equally to intermediaries
as well as ultimate destinations of an XMLP envelope.</p>
</dd>
<dt class="label"><a name="z700a"></a>R700a Requirement for Extensibility</dt>
<dd>
<p id="z700">The XMLP specification must define a mechanism or
mechanisms that allow applications to submit application-specific content or
information for delivery by XMLP. In forming the standard for the mechanisms,
the XMLP specification may consider support for:</p>
<ul>
<li>
<p>carrying application specific payloads inside the XMLP
envelope,</p>
</li>
<li>
<p>referring to application specific payloads outside the
XMLP envelope,</p>
</li>
<li>
<p>carrying nested XMLP envelopes as application specific
data within the XMLP envelope,</p>
</li>
<li>
<p>referring to XMLP envelopes as application specific data
outside the XMLP envelope</p>
</li>
</ul>
<p>Regarding the handling of binary data in particular, the XML
Protocol WG Charter <a href="#xmlp-charter">[3]</a> has the following to say:</p>
<p>
<em>
<b>Charter:</b>
"Note that XML Namespaces provide a flexible
and lightweight mechanism for handling language mixing as long as those
languages are expressed in XML. In contrast, there is only very rudimentary
support (base-64 encodings etc.) for including data languages expressed in
binary formats. Such formats include commonly used image formats like PNG, JPEG
etc. Although it is inconceivable to imagine a Web without such data formats,
it is not considered a priority of this Working Group to solve this problem.
This is in part because other organizations (e.g.
<a href="http://www.ebxml.org">ebXML</a> and
<a href="http://www.rosettanet.org">RosettaNet</a>) are already addressing the issue
using an approach based on MIME multipart. The Working Group can consider
solutions proposed by other groups as a matter of low priority, if there is
sufficient interest."
</em>
</p>
</dd>
<dt class="label"><a name="z700b"></a>R700b Requirement for Extensibility</dt>
<dd>
<p>To manage the mechanisms, the XMLP specification must define a
set of directives which will unambiguously indicate to an XMLP processor which
extensions are optional and which are mandatory so that it can:</p>
<ul>
<li>
<p>process all of the extensions in an XMLP envelope or
fail,</p>
</li>
<li>
<p>process a subset of the extensions in an XMLP envelope or
fail.</p>
</li>
</ul>
</dd>
<dt class="label"><a name="z700c"></a>R700c Requirement for Extensibility</dt>
<dd>
<p>In both cases above, the XMLP processor must fail in a
standard and predictable fashion.</p>
</dd>
<dt class="label"><a name="z702"></a>R702 Requirement for Evolution</dt>
<dd>
<p>The XMLP specification must define the concept of protocol
evolution and define a mechanism or mechanisms for identifying XMLP revisions.
This mechanism or mechanisms must ensure that an XMLP processor, by simple
inspection of an XMLP envelope, may determine whether or not the envelope is
compatible with its processing ability. The specification must define the
concepts of backwards compatible and backwards incompatible evolution.</p>
</dd>
<dt class="label"><a name="z703a"></a>R703a Requirement for Encapsulation of Error
Information</dt>
<dd>
<p>The XMLP specification must define a means to convey error
information as a fault. The capability of XMLP carrying a fault message must
not depend on any particular protocol binding.</p>
</dd>
<dt class="label"><a name="z703b"></a>R703b Requirement for Encapsulation of
Status</dt>
<dd>
<p>The XMLP specification must define a mechanism or mechanisms
to allow the transfer of status information within an XMLP message without
resort to use of XMLP fault messages or dependence on any particular
interaction model.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="N1136"></a>4.4 Intermediaries</h3>
<p>
<em>
<b>Charter:</b>
"Intermediaries are essential parts of building
distributed systems that scale to the Web. Intermediaries can act in different
capacities ranging from proxies, caches, store-and-forward hops, to gateways.
Experience from HTTP <a href="#RFC2616">[6]</a> and other protocols has shown that
intermediaries cannot be implicitly defined but must be an explicit part of the
message path model for any data encapsulation language. Therefore, the Working
Group must ensure that the data encapsulation language supports composability
both in the vertical (within a peer) as well as in the horizontal (between
peers)."
</em>
</p>
<p>Because XMLP separates the message envelope from the transport
binding, two types of intermediaries are possible; transport intermediaries and
processing intermediaries.</p>
<div class="div3">
<h4><a name="N1137"></a>4.4.1 Transport Intermediaries</h4>
<p>Transport intermediaries are interposed by a transport binding, as
part of the message exchange pattern that it implies. They do not define a
processing model for messages; they only operate as part of the transport
binding, as a message routing mechanism and cannot be addressed from within an
XMLP envelope.</p>
<dl>
<dt class="label"><a name="z803"></a>R803</dt>
<dd>
<p>XMLP must not preclude the use of transport bindings that
define transport intermediary roles such as store-and-forward, proxy and
gateway.</p>
</dd>
</dl>
</div>
<div class="div3">
<h4><a name="N1138"></a>4.4.2 Processing Intermediaries</h4>
<p>Processing intermediaries are full XMLP processors; they process
the message, but are not the ultimate recipient of it. They may be colocated
with transport intermediaries, using them as a routing mechanism, or they may
use in-message routing mechanisms.</p>
<dl>
<dt class="label"><a name="z811"></a>R811</dt>
<dd>
<p>XMLP must define and accommodate processing
intermediaries.</p>
</dd>
</dl>
<p>To enable the interposition of processing intermediaries into the
message path, two core requirements must be met:</p>
<dl>
<dt class="label"><a name="z806"></a>R806</dt>
<dd>
<p>Targeting - XMLP must define mechanisms that allow XMLP
processors, including intermediaries, to identify XMLP extensions which they
are eligible to process.</p>
</dd>
<dt class="label"><a name="z808"></a>R808</dt>
<dd>
<p>Reporting - XMLP must enable the generation of status and/or
error messages by processing intermediaries, and enable propagation and proper
identification of status and/or error messages through processing
intermediaries.</p>
</dd>
</dl>
<p>In addition</p>
<dl>
<dt class="label"><a name="z802"></a>R802</dt>
<dd>
<p>XMLP must also enable processing intermediaries to locate
and process XMLP extensions intended for them without processing the entire
message.</p>
</dd>
</dl>
</div>
</div>
<div class="div2">
<h3><a name="N400"></a>4.5 Data Representation</h3>
<p>
<em>
<b>Charter:</b>
"With the introduction of XML and Resource
Description Framework (RDF) schema languages, and the existing capabilities of
object and type modeling languages such as Unified Modeling Language (UML),
applications can model data at either a syntactic or a more abstract level. In
order to propagate these data models in a distributed environment, it is
required that data conforming to a syntactic schema can be transported
directly, and that data conforming to an abstract schema can be converted to
and from XML for transport."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"The Working Group should propose a mechanism for
serializing data representing non-syntactic data models in a manner that
maximizes the interoperability of independently developed Web applications.
Furthermore, as data models change, the serialization of such data models may
also change. Therefore it is important that the data encapsulation and data
representation mechanisms are designed to be orthogonal."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"Examples of relationships that will have to be
serialized include subordinate relationships known from attachments and
manifests. Any general mechanism produced by the Working Group for serializing
data models must also be able to support this particular case."
</em>
</p>
<dl>
<dt class="label"><a name="z400"></a>R400</dt>
<dd>
<p>The XMLP data encapsulation and data representation mechanisms
must be orthogonal.</p>
</dd>
<dt class="label"><a name="z401"></a>R401</dt>
<dd>
<p>The XMLP data representation must support using XML Schema
simple and complex types <a href="#XMLSchemaP1">[8]</a>
<a href="#XMLSchemaP2">[9]</a>.</p>
</dd>
<dt class="label"><a name="z402"></a>R402</dt>
<dd>
<p>The XMLP data representation must be able to serialize data
based on data models not directly representable by XML Schema simple and
complex types. These data models include object graphs and directed labeled
graphs. It must be possible to reconstruct the original data from the data
representation.</p>
</dd>
<dt class="label"><a name="z403"></a>R403</dt>
<dd>
<p>Data serialized according to the XMLP data representation may
contain references to data outside the serialization. These references must be
Uniform Resource Identifiers (URIs) <a href="#RFC2396">[5]</a>.</p>
</dd>
<dt class="label"><a name="z404"></a>R404</dt>
<dd>
<p>The XMLP data representation must be able to encode arrays
which may be nested.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="N1423"></a>4.6 Protocol Bindings</h3>
<p>
<em>
<b>Charter:</b>
"A mechanism for using HTTP transport in the context
of an XML Protocol. This does not mean that HTTP is the only transport
mechanism that can be used for the technologies developed, nor that support for
HTTP transport is mandatory. This component merely addresses the fact that HTTP
transport is expected to be widely used, and so should be addressed by this
Working Group."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"Mapping onto existing application layer protocols
may lead to scalability problems, security problems and semantic complications
when the application semantics defined by those protocols interfere with the
semantics defined by an XML Protocol. The WG may consider issuing a warning
about the possible problems of reusing non-safe "transports" like SMTP and
others. A mapping onto transport services other than HTTP will only be started
if enough interest is shown and time is available."
</em>
</p>
<p>
<em>
<b>Charter:</b>
"General transport issues were investigated by the
HTTP-NG Activity, which designed a general transport mechanism for handling
out-of-order delivery of message streams between two peers. While we do
strongly encourage work to be undertaken in this area, it is expected that work
in this area will be done in collaboration with the
<a href="http://www.ietf.org">IETF</a> and not as part of this Working
Group"
</em>
</p>
<dl>
<dt class="label"><a name="z600"></a>R600</dt>
<dd>
<p>The XMLP specification must not mandate any dependency on
specific features or mechanisms provided by a particular transport protocol
beyond the basic requirement that the transport protocol must have the ability
to deliver the XMLP envelope as a whole unit. This requirement does not
preclude a mapping or binding to a transport protocol taking advantages of such
features. It is intended to ensure that the basic XMLP specification will be
transport neutral.</p>
</dd>
<dt class="label"><a name="z604"></a>R604</dt>
<dd>
<p>The XMLP specification must consider the scenario where an
XMLP message may be routed over possibly many different transport or
application protocols as it moves between intermediaries on the message path.
This requirement implies it must be possible to apply many transport or
application protocol bindings to the XMLP message without information loss from
the XMLP message content.</p>
</dd>
<dt class="label"><a name="z608"></a>R608</dt>
<dd>
<p>The XMLP binding mechanism should not preclude the possibility
of constructing bindings to protocols that provide a security mechanism.</p>
<p>Typical examples of such protocols are SSL providing a secure
channel,and S/MIME which provides a secure wrapper. It should be possible to
specify XMLP bindings for such security protocols.</p>
</dd>
<dt class="label"><a name="z609"></a>R609</dt>
<dd>
<p>The XMLP specification may mandate the use of a specific
character encoding, such as UTF-8, at some point in the future.</p>
<p>The Working Group is aware of the complexity resulting in the
use of a large set of character encodings and is actively seeking feedback in
this area. Until all the feedback has been evaluated, the Working Group will
not make a decision in favor of restriction.</p>
</dd>
<dt class="label"><a name="z612"></a>R612</dt>
<dd>
<p>The XMLP specification must provide a normative description of
the default binding of XMLP to HTTP <a href="#RFC2616">[6]</a>. This binding,
while normative, is not to be exclusive. The binding provided by the Working
Group will respect the semantics of HTTP and will demonstrate that it can
co-exist with existing HTTP/1.0 and HTTP/1.1 implementations.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="N1595"></a>4.7 Convention for RPC</h3>
<p>
<em>
<b>Charter:</b>
"A convention for the content of the envelope when
used for RPC (Remote Procedure Call) applications. The protocol aspects of this
should be coordinated closely with the
<a href="http://www.ietf.org">IETF</a> and make an effort to leverage any work
they are doing"
</em>
</p>
<dl>
<dt class="label"><a name="z200"></a>R200</dt>
<dd>
<p>XMLP must contain a convention for representing calls and
replies between RPC (Remote Procedure Call) applications and services. The
conventions must include the following:</p>
<ol>
<li>
<p>Complete and unique identification, by means of URI syntax
<a href="#RFC2396">[5]</a>, of the program, service or object and procedure or
method to be called.</p>
</li>
<li>
<p>Enable support for matching response messages to request
messages for cases in which matching is not provided by the underlying protocol
binding.</p>
</li>
<li>
<p>The ability to specify the parameters to a call in a
request message and the results of a call in a reply messages.</p>
</li>
<li>
<p>Provisions for specifying errors in a reply message (see
also <b>[<a href="#z703a">R703a Requirement for Encapsulation of Error
Information</a>]</b> and <b>[<a href="#z703b">R703b Requirement for Encapsulation of
Status</a>]</b>)</p>
</li>
</ol>
<p>Where possible, an attempt will be made to leverage any
related work done by the
<a href="http://www.ietf.org">IETF</a>.</p>
</dd>
<dt class="label"><a name="z201"></a>R201</dt>
<dd>
<p>The RPC conventions within XMLP should use the Data
Representation model discussed in <a href="#N400"><b>4.5 Data Representation</b></a> to represent parameters
to a call in the request message and results of the call in the reply message.
It must be convenient to create straightforward mappings of the data types to a
wide variety of widely deployed programming languages and object systems.</p>
</dd>
<dt class="label"><a name="z202"></a>R202</dt>
<dd>
<p>XMLP should allow applications to include custom encodings for
data types used for parameters and results in RPC messages.</p>
</dd>
</dl>
</div>
</div>
<div class="div1">
<h2><a name="N2100"></a>5. Requirements from other W3C WGs</h2>
<p>These are requirements submitted by other W3C Working Groups and
Activities.</p>
<div class="div2">
<h3><a name="N2200"></a>5.1 XForms Requirements</h3>
<p>XForms models the data to be obtained from the user, specifies how a
user interface for obtaining the data is declared using XHTML markup, and
finally specifies how the populated data is shipped backed to the server. The
[SEND] subgroup is responsible for the interactions between the XForms client
and the backend server.</p>
<p>The work on [SEND] could be a replacement for the various methods
for posting data to an HTTP server such as application/x-www-form-urlencoded or
multipart/form-data.</p>
<p>Requirements:</p>
<ol>
<li>
<p>An XForms client needs to send and receive well-formed XML data
that has been defined through the XForms specification. For example, XML data
will be "sent" when the user agent is done filling out an XForm or XML data
will be "received" when a server ships out initial values for populating a
form.</p>
</li>
<li>
<p>An XForms client needs to send/receive partially completed XML
data to/from the server for persistence. This functionality will allow a user
agent to "save" or "load" a form in progress. Therefore, the XML data may not
fully conform to a schema when only partially completed.</p>
</li>
<li>
<p>An XForms client needs to be able to send/receive arbitrary
binary content along with the XML data. This will be used to support features
such as the "file upload" feature available in many WWW browsers. There needs
to be support for both 'in-band' (i.e. the binary data is within the XML data
in an XML compatible encoding such as base64) and 'out-of-band' data (i.e. the
binary data is available at some other location, and the XML data refers to the
other location).</p>
</li>
</ol>
</div>
<div class="div2">
<h3><a name="N1573"></a>5.2 P3P Requirements</h3>
<p>These are the requirements that the XML Protocol WG
<a href="#xmlp-wg">[2]</a> has received from the
<a href="http://www.w3.org/P3P/">P3P WG</a>
<a href="http://lists.w3.org/Archives/Member/w3c-xml-protocol-wg/2000Oct/0065.html">:</a>
</p>
<ul>
<li>
<p>It must be possible to associate a P3P Privacy Policy with an
XMLP message.</p>
</li>
</ul>
</div>
<div class="div2">
<h3><a name="L5908"></a>5.3 RDF and UML Requirements</h3>
<p>The XML Protocol WG has not directly received a set of requirements
from the
<a href="http://www.w3.org/RDF/">RDF WG</a> and from the UML group similar to what
was received from the
<a href="#N1573">P3P</a> and the
<a href="#N2200">XForms WGs</a>.
However, the WG believes that <b>[<a href="#z402">R402</a>]</b> and
<a href="http://www.w3.org/2002/10/XML-Protocol-Charter#representation">section
1.4 of the XML Protocol WG charter</a> addresses the primary concerns of
these groups. The WG has dealt with these concerns as part of
<a href="http://www.w3.org/2000/xp/Group/xmlp-issues#x29">issue 29</a>.</p>
</div>
</div>
<div class="div1">
<h2><a name="N2690"></a>6. Usage Scenarios</h2>
<p>Usage scenarios are intended to provide representative examples of
situations where XMLP might be applicable. The purpose of usage scenarios is to
help ensure that XMLP is capable of dealing with applications and services
actually seen in the Web. Hence, usage scenario specifications should be at a
coarse-grain level of an end user's desired XML document/message interchange,
rather than at a detailed, implementation or transport specific level. Usage
scenarios often make assumptions about the specific environments in which the
use cases are described that the requirements cannot.</p>
<p>In other words, the requirements are explicitly targeted to the design
of XMLP; usage scenarios are targeted to systems in which XMLP is most likely
part of an overall solution. Not all requirements need to be referenced by an
example usage scenario, since, in addition to higher-level, application
specific requirements for use, there are internal, architectural requirements
independent of any specific higher-level use (e.g., using XML, schemas, and
namespaces imposes certain requirements irrespective of use).</p>
<dl>
<dt class="label"><a name="s1"></a>S1 Fire-and-forget to single receiver</dt>
<dd>
<p>A sender wishes to send an unacknowledged message to a single
receiver (e.g. send a stock price update every 15 minutes)</p>
<div class="note"><p class="prefix"><b>Note:</b></p>
<p>S1 Originates from splitting the
<a href="http://www.ebxml.org">ebXML</a> use case 1.1 into 2 scenarios (S1 and
S2).</p>
</div>
</dd>
<dt class="label"><a name="s2"></a>S2 Fire-and-forget to multiple receivers</dt>
<dd>
<p>A sender wishes to send unacknowledged messages to a set of
receivers (e.g. send a stock price update every 15 minutes)</p>
<div class="note"><p class="prefix"><b>Note:</b></p>
<p>S2 Originates from splitting the
<a href="http://www.ebxml.org">ebXML</a> use case 1.1 into 2 scenarios (S1 and
S2). Note that S2 may be decomposed into Multiple instances of S1 under the
control of some "higher-level" process such as multicast or
publish/subscribe.</p>
</div>
</dd>
<dt class="label"><a name="s3"></a>S3 Request-response</dt>
<dd>
<p>Two parties wish to conduct electronic business by the exchange
of business documents. The sending party packages one or more documents into a
request message which is then sent to the receiving party. The receiving party
then processes the message contents and responds to the sending party. Examples
of the sending party's documents may be purchase order requests, manufacturing
information and patient healthcase information. Examples of the receiving
party's responses may include order confirmations, change control information
and contractual acknowledgements.</p>
</dd>
<dt class="label"><a name="s4"></a>S4 Remote Procedure Call (RPC)</dt>
<dd>
<p>The sender invokes the service by passing parameters that are
serialised into a message for transmission to the receiving server.</p>
</dd>
<dt class="label"><a name="s5"></a>S5 Request with acknowledgement</dt>
<dd>
<p>A sender wishes to reliably exchange data with a receiver. It
wishes to be notified of the status of the data delivery to the receiver. The
status may take the form of:</p>
<ol>
<li>
<p>The data has been successfully delivered to the receiver,
or</p>
</li>
<li>
<p>Some failure has occurred which prevents the sucessful
delivery to the receiver.</p>
</li>
</ol>
<div class="note"><p class="prefix"><b>Note:</b></p>
<p>This scenario does not imply that reliable message delivery
will be supported by the XMLP core specification.</p>
</div>
</dd>
<dt class="label"><a name="s6"></a>S6 Request with encrypted payload</dt>
<dd>
<p>A sender wishes to exchange data with a receiver and has agreed
to encrypt the payload. The sending and receiving applications agree on the
encryption methodology. Data is encrypted by the originating application and
sent to the receiver via XMLP.The data reaches the receiving application
untouched, and may then be decrypted in the agreed-upon manner.</p>
</dd>
<dt class="label"><a name="s7"></a>S7 Third part intermediary</dt>
<dd>
<p>A blind auction marketplace serves as a broker between buyers
and suppliers. Buyers submit their requirements to the marketplace hub, which
broadcasts this information to multiple suppliers. Suppliers respond to the
marketplace hub where the information is logged and ultimately delivered to the
buyer.</p>
</dd>
<dt class="label"><a name="s8"></a>S8 Conversational message exchange</dt>
<dd>
<p>Two partners are engaged in a long-running process which
involves multiple message exchanges. Examples of such processes may be complex
supply chain management, dynamic manufacturing scheduling or information
retrieval. There may be multiple instances of the same process in progress
between the same two partners.</p>
</dd>
<dt class="label"><a name="s10"></a>S10 Message header and payload encryption</dt>
<dd>
<p>Two trading partners engaged in a message exchange may agree to
cryptographically sign and verify either the message header, the routing
header(s) and/ or the payload. The sender or originating application may
perform the siging of the payload. The sending message extension signs the
message header. A routing header may be appended to the message header. The
routing header may also be signed by a message service extension.</p>
</dd>
<dt class="label"><a name="s11"></a>S11 Communication via multiple intermediaries</dt>
<dd>
<p>An intermediary forwards a message to the ultimate receiver on
behalf of an initial sender. The initial sender wishes to enforce the
non-repudiation property of the route. Any intermediate message service
extension that appends a routing message must log the routing header
information. Signed routing headers and the message headers must be logged at
the intermediary which passes the message to the ultimate receiver to provide
the evidence of non-repudiation.</p>
</dd>
<dt class="label"><a name="s17"></a>DS17 Asynchronous messaging</dt>
<dd>
<p>A sender sends a message asynchronously to a receiver expecting
some response at a later time. The sender tags the request with an identifier
allowing the response to be correlated with the originating request. The sender
may also tag the message with an identifier for another service (other than the
originating sender) which will be the recipient of the response.</p>
</dd>
<dt class="label"><a name="s19"></a>S19 Sending non-XML data</dt>
<dd>
<p>A digital camera wishes to transmit image data over a wireless
link using XMLP to a remote server. The binary image data (non-XML) accompanies
the message. The digital camara represents a situation in which connections
from the receiver to the sender may not be permitted due to device limitations
or firewalls.</p>
</dd>
<dt class="label"><a name="s20"></a>S20 Multiple asynchronous responses</dt>
<dd>
<p>An application requests some information from a server, which is
returned at a later time in multiple responses. This can be because the
requested information was not available all at once (e.g., distributed web
searches). (based on <a href="#mail1">[13]</a>)</p>
</dd>
<dt class="label"><a name="s21"></a>S21 Incremental parsing/processing of XMLP
messages</dt>
<dd>
<p>An XMLP sender generates a lengthy XMLP message that is
incrementally transmitted and received by an XMLP receiver. The XMLP receiver
processes the body as it is received (e.g., employing a SAX-style XML parser on
the body as it arrives). Note that the entire message need not be present at
one time at any point in its existence.</p>
<p>This would be particularly helpful for memory-limited
processors. It is also very efficient for services which are consistent with
incremental, real-time transformations of the data, direct archiving of
received data, etc. It would also be useful in scenarios in which voluminous
body data can be directly transduced into application data structures or events
by an XMLP (module) processor. In particular, there is no need for the explicit
construction of a DOM model of the data. Support for XMLP data models might
still be possible even with incremental processing if the models are
incrementally constructible (copied in its entirety from <a href="#mail2">[14]</a>)</p>
</dd>
<dt class="label"><a name="s23"></a>S23 Event notification</dt>
<dd>
<p>An application subscribes to notifications of certain named
events from an event source. When such events occur, notifications are sent
back to the originating application (first party notification) or to another
application (third party notification). For example, an application can
subscribe to notification of various aspects of a printer's status (e.g.,
running out of paper, ink etc.). The notifications of such events could be
delivered to a management application (based on: See item 2 of
<a href="#mail3">[15]</a>)</p>
</dd>
<dt class="label"><a name="s24"></a>DS24 Caching</dt>
<dd>
<p>Some applications may wish to make caching possible for latency,
bandwidth use or other gains in efficiency. To enable this, it should be
possible to assign cacheability in a variety of circumstances. For example,
"read" caching might be used to store messages at intermediaries for reuse in
the response phase of the request/response message exchange pattern. Such
caching might be on the scope of an entire message, an XMLP module, or scoped
to individual XMLP module elements.</p>
<p>Similarly, "write" caching may be useful in situations when a
request message in a request/response message exchange pattern (as well as
similar messages in other message exchange patterns) does not need to be
immediately forwarded or responded to. Such cachability might be scoped by
different methods, as outlined above.</p>
<p>Cacheability scoped by different elements might be associated by
an attribute to the target element, through use of XML Query or XPath to
describe the target elements in a header, or implied by the document schema,
for example.</p>
<p>Cacheability mechanisms applied to messages, bodies or elements
might include time-to-live (delta time), expiry (absolute time), entity
validation, temporal validation, subscription to invalidation services, and
object update/purge.</p>
<p>Finally, some applications may be capable of describing the
dependencies and relationships between message elements. For example, a
response element may be applicable to a wide range of requests; it would be
beneficial to describe this element's relationship with request elements, so
that it may satisfy a wide range of requests in an economical fashion.
Similarly, the presence of a particular element may be a trigger for a
cacheability mechanism to be applied to another element, such as validation or
invalidation (see also <a href="#mail4">[16]</a>)</p>
</dd>
<dt class="label"><a name="s805"></a>S805 Routing</dt>
<dd>
<p>A developer wishes to force an explicit message path through
certain intermediaries - for instance, he might use an anonymizing intermediary
to make a call to a specified remote service without allowing the target
service to track the identity/IP of the caller. In this case, the intermediary
is responsible for calling the target service and returning the results to the
caller, using its own authentication credentials if any are required by the
target service.</p>
</dd>
<dt class="label"><a name="s807"></a>S807 Tracking</dt>
<dd>
<p>A service provider wishes to track incoming messages to see
exactly which processing intermediaries have touched it by the time it arrives
at its destination. It therefore requires a tracking extension to be included
by all clients, and by any processing intermediaries along the message paths
from the clients to the server.</p>
</dd>
<dt class="label"><a name="s809"></a>S809 Caching with Expiration</dt>
<dd>
<p>BizCo updates their online price catalog every morning at 8AM.
Therefore, when remote clients access their XMLP inventory service, clients and
intermediaries may cache the results of any price queries until 8AM the next
day.</p>
</dd>
<dt class="label"><a name="s810"></a>S810 QoS</dt>
<dd>
<p>An XMLP sender (not necessarily the initial XMLP sender) wants
the XMLP message to be handled with specific quality of service as it traverses
the XMLP message path to include multiple XMLP Processing intermediaries.
Information in the XMLP message is used to select appropriate QoS mechanisms
(e.g.,
<a href="http://www.ietf.org/html.charters/rsvp-charter.html">RSVP</a>,
<a href="http://www.ietf.org/html.charters/OLD/diffserv-charter.html">Diffserv</a>,
<a href="http://www.ietf.org/html.charters/mpls-charter.html">MPLS</a>, etc.). Selection of QoS may be
constrained by
<a href="http://www.ietf.org/html.charters/policy-charter.html">QoS policies</a>,
<a href="http://www.dmtf.org/about/working/sla.php">Service Level Agreements</a> (SLAs),
<a href="http://www.ist-tequila.org/">Service Level Specifications</a> (SLS).</p>
</dd>
</dl>
</div>
<div class="div1">
<h2><a name="N2678"></a>7. References</h2>
<dl>
<dt class="label"><a name="xmlp-activity"></a>[1] </dt><dd>Web Services
Activity (See <a href="http://www.w3.org/2002/ws/Activity.html">http://www.w3.org/2002/ws/Activity.html</a>.)</dd>
<dt class="label"><a name="xmlp-wg"></a>[2] </dt><dd>XML Protocol Working
Group (See <a href="http://www.w3.org/2000/xp/Group/">http://www.w3.org/2000/xp/Group/</a>.)</dd>
<dt class="label"><a name="xmlp-charter"></a>[3] </dt><dd>XML
Protocol Working Group Charter (See <a href="http://www.w3.org/2002/10/XML-Protocol-Charter">http://www.w3.org/2002/10/XML-Protocol-Charter</a>.)</dd>
<dt class="label"><a name="xml-dist-app"></a>[4] </dt><dd>XML
Protocol Discussion Archive (See <a href="http://lists.w3.org/Archives/Public/xml-dist-app/">http://lists.w3.org/Archives/Public/xml-dist-app/</a>.)</dd>
<dt class="label"><a name="RFC2396"></a>[5] </dt><dd>IETF "RFC 2396: Uniform Resource
Identifiers (URI): Generic Syntax", T. Berners-Lee, R. Fielding, L. Masinter,
August 1998. (See <a href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a>.)</dd>
<dt class="label"><a name="RFC2616"></a>[6] </dt><dd>IETF "RFC 2616: Hypertext Transfer
Protocol -- HTTP/1.1", R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, T.
Berners-Lee, January 1997. (See <a href="http://www.ietf.org/rfc/rfc2616.txt">http://www.ietf.org/rfc/rfc2616.txt</a>.)</dd>
<dt class="label"><a name="soap11"></a>[7] </dt><dd>W3C Note "Simple Object Access Protocol
(SOAP) 1.1", Don Box, David Ehnebuske, Gopal Kakivaya, Andrew Layman, Noah
Mendelsohn, Henrik Nielsen, Satish Thatte, Dave Winer, 8 May 2000. (See <a href="http://www.w3.org/TR/SOAP/">http://www.w3.org/TR/SOAP/</a>.)</dd>
<dt class="label"><a name="XMLSchemaP1"></a>[8] </dt><dd>W3C
Recommendation "XML Schema Part 1: Structures", Henry S. Thompson, David Beech,
Murray Maloney, Noah Mendelsohn, 2 May 2001. (See <a href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/">http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/</a>.)</dd>
<dt class="label"><a name="XMLSchemaP2"></a>[9] </dt><dd>W3C
Recommendation "XML Schema Part 2: Datatypes", Paul V. Biron, Ashok Malhotra, 2
May 2001. (See <a href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/">http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/</a>.)</dd>
<dt class="label"><a name="XMLNS"></a>[10] </dt><dd>W3C
Recommendation "Namespaces in XML", Tim Bray, Dave Hollander, Andrew Layman, 14
January 1999. (See <a href="http://www.w3.org/TR/1999/REC-xml-names-19990114/">http://www.w3.org/TR/1999/REC-xml-names-19990114/</a>.)</dd>
<dt class="label"><a name="XML"></a>[11] </dt><dd>W3C Recommendation
"Extensible Markup Language (XML) 1.0 (Second Edition)", Tim Bray, Jean Paoli,
C. M. Sperberg-McQueen, Eve Maler, 6 October 2000. (See <a href="http://www.w3.org/TR/2000/REC-xml-20001006">http://www.w3.org/TR/2000/REC-xml-20001006</a>.)</dd>
<dt class="label"><a name="w3c-conformance"></a>[12] </dt><dd>W3C
Conformance requirements (W3C Members only) (See <a href="http://www.w3.org/Guide/Conformance.html">http://www.w3.org/Guide/Conformance.html</a>.)</dd>
<dt class="label"><a name="mail1"></a>[13] </dt><dd>Mail 1 (See <a href="http://lists.w3.org/Archives/Public/xml-dist-app/2000Dec/0208.html">http://lists.w3.org/Archives/Public/xml-dist-app/2000Dec/0208.html</a>.)</dd>
<dt class="label"><a name="mail2"></a>[14] </dt><dd>Mail 2 (See <a href="http://lists.w3.org/Archives/Public/xml-dist-app/2000Dec/0204.html">http://lists.w3.org/Archives/Public/xml-dist-app/2000Dec/0204.html</a>.)</dd>
<dt class="label"><a name="mail3"></a>[15] </dt><dd>Mail 3 (See <a href="http://lists.w3.org/Archives/Public/xml-dist-app/2001Jan/0070.html">http://lists.w3.org/Archives/Public/xml-dist-app/2001Jan/0070.html</a>.)</dd>
<dt class="label"><a name="mail4"></a>[16] </dt><dd>Mail 4 (See <a href="http://lists.w3.org/Archives/Public/xml-dist-app/2001Jan/0109.html">http://lists.w3.org/Archives/Public/xml-dist-app/2001Jan/0109.html</a>.)</dd>
</dl>
</div>
</div>
<div class="back">
<div class="div1">
<h2><a name="N2672"></a>A. Acknowledgments (Non-Normative)</h2>
<p>The WG thanks all participants of the
<a href="mailto:xml-dist-app@w3.org">xml-dist-app@w3.org</a> mailing list (Archives
<a href="#xml-dist-app">[4]</a>) for directly and indirectly contributing to this
document.</p>
</div>
</div>
</body></html>