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<h1><a name="title" id="title"></a>XQuery Update Facility 1.0
Requirements</h1>
<h2><a name="w3c-doctype" id="w3c-doctype"></a>W3C Working Group
Note 25 January 2011</h2>
<dl>
<dt>This version:</dt>
<dd><a href=
"http://www.w3.org/TR/2011/NOTE-xquery-update-10-requirements-20110125/">
http://www.w3.org/TR/2011/NOTE-xquery-update-10-requirements-20110125/</a></dd>
<dt>Latest version:</dt>
<dd><a href=
"http://www.w3.org/TR/xquery-update-10-requirements/">http://www.w3.org/TR/xquery-update-10-requirements/</a></dd>
<dt>Previous version:</dt>
<dd><a href=
"http://www.w3.org/TR/2008/CR-xquery-update-10-requirements-20080314/">
http://www.w3.org/TR/2008/CR-xquery-update-10-requirements-20080314/</a></dd>
<dt>Editors:</dt>
<!--xmlspec, match="author"-->
<dd>Don Chamberlin, IBM Almaden Research Center <a href=
"mailto:chamberlin@almaden.ibm.com">&lt;chamberlin@almaden.ibm.com&gt;</a></dd>
<!--xmlspec, match="author"-->
<dd>Jonathan Robie, Red Hat <a href=
"mailto:jonathan.robie@redhat.com">&lt;jonathan.robie@redhat.com&gt;</a></dd>
</dl>
<p class="copyright"><a href=
"http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>&#160;©&#160;2011&#160;<a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup>
(<a href="http://www.csail.mit.edu/"><acronym title=
"Massachusetts Institute of Technology">MIT</acronym></a>, <a href=
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<a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved.
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<hr />
<div>
<h2><a name="abstract" id="abstract"></a>Abstract</h2>
<p>This document specifies goals and requirements for the XQuery
Update Facility.</p>
</div>
<div>
<h2><a name="status" id="status"></a>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 is a <a href=
"http://www.w3.org/2005/10/Process-20051014/tr.html#tr-end">Working
Group Note</a> as described in the <a href=
"http://www.w3.org/2005/10/Process-20051014/tr.html">Process
Document</a>. It has been developed by the W3C <a href=
"http://www.w3.org/XML/Query/">XML Query Working Group</a>, which
is part of the <a href="http://www.w3.org/XML/Activity">XML
Activity</a>.</p>
<p>This document includes, for each requirement, a corresponding
status, indicating the current situation of the requirement in
<a href="http://www.w3.org/TR/xquery-update-10/">XQuery Update
Facility 1.0</a> at the time that it was issued as a final
Recommendation on 22 February 2011. Three status levels are
used:</p>
<dl>
<dt class="label">"Green" status</dt>
<dd>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> This indicates that the requirement, according to
its original formulation, has been completely met. Optional
clarificatory text may follow.</p>
</dd>
<dt class="label">"Yellow" status</dt>
<dd>
<p><img src="http://www.w3.org/Icons/yellow-ball.gif" alt=
"yellow status" /> This indicates that the requirement has been
partially met according to its original formulation. When this
status is indicated, explanatory text is provided to better clarify
the current scope of the requirement.</p>
</dd>
<dt class="label">"Red" status</dt>
<dd>
<p><img src="http://www.w3.org/Icons/red-ball.gif" alt=
"red status" /> This indicates that the requirement, according to
its original formulation, has not been met. If this is the case,
explanatory text is provided.</p>
</dd>
</dl>
<p>No substantive changes have been made to this specification
since its publication as a Proposed Recommendation.</p>
<p>Please report errors in this document using W3C's <a href=
"http://www.w3.org/Bugs/Public/">public Bugzilla system</a>
(instructions can be found at <a href=
"http://www.w3.org/XML/2005/04/qt-bugzilla">http://www.w3.org/XML/2005/04/qt-bugzilla</a>).
If access to that system is not feasible, you may send your
comments to the W3C XSLT/XPath/XQuery public comments mailing list,
<a href=
"mailto:public-qt-comments@w3.org">public-qt-comments@w3.org</a>.
It will be very helpful if you include the string “[UPDreq]” in the
subject line of your report, whether made in Bugzilla or in email.
Please use multiple Bugzilla entries (or, if necessary, multiple
email messages) if you have more than one comment to make. Archives
of the comments and responses are available at <a href=
"http://lists.w3.org/Archives/Public/public-qt-comments/">http://lists.w3.org/Archives/Public/public-qt-comments/</a>.</p>
<p>Publication as a <a href=
"http://www.w3.org/2005/10/Process-20051014/tr.html#tr-end">Working
Group Note</a> does not imply endorsement by the W3C Membership. At
the time of publication, work on this document was considered
complete and no further revisions are anticipated. It is a stable
document and may be used as reference material or cited from
another document. However, this document may be updated, replaced,
or made obsolete by other documents at any time.</p>
<p>This document was produced by a group operating under the
<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5
February 2004 W3C Patent Policy</a>. W3C maintains a <a href=
"http://www.w3.org/2004/01/pp-impl/18797/status#disclosures">public
list of any patent disclosures</a> made in connection with the
deliverables of the group; that page also includes instructions for
disclosing a patent. An individual who has actual knowledge of a
patent which the individual believes contains <a href=
"http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">
Essential Claim(s)</a> must disclose the information in accordance
with <a href=
"http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">
section 6 of the W3C Patent Policy</a>.</p>
</div>
<div class="toc">
<h2><a name="contents" id="contents"></a>Table of Contents</h2>
<p class="toc">1 <a href="#d3e185">Goals</a><br />
2 <a href="#d3e192">Usage Scenarios</a><br />
3 <a href="#d3e236">Requirements</a><br />
&#160;&#160;&#160;&#160;3.1 <a href="#d3e239">Terminology</a><br />
&#160;&#160;&#160;&#160;3.2 <a href="#d3e274">General
Requirements</a><br />
&#160;&#160;&#160;&#160;3.3 <a href="#d3e377">Relationship to
XQuery 1.0</a><br />
&#160;&#160;&#160;&#160;3.4 <a href="#id-update-functionality">XML
Query Update Functionality</a><br />
&#160;&#160;&#160;&#160;3.5 <a href="#d3e646">Transaction
characteristics</a><br /></p>
<h3><a name="appendices" id="appendices"></a>Appendix</h3>
<p class="toc">A <a href="#d3e735">References</a><br /></p>
</div>
<hr />
<div class="body">
<div class="div1">
<h2><a name="d3e185" id="d3e185"></a>1 Goals</h2>
<p>This document describes the requirements for the XQuery Update
Facility. <a href="#xquery">[XQuery 1.0]</a> provides queries, but
has no support for adding new values or changing existing values.
The XML Query Working Group intends to add support for updates in a
future version of XQuery.</p>
</div>
<div class="div1">
<h2><a name="d3e192" id="d3e192"></a>2 Usage Scenarios</h2>
<p>The following usage scenarios describe how the XQuery Update
Facility may be used in various environments, and represent a wide
range of activities and needs that illustrate the problem space to
be addressed. They are intended to be used as design cases during
the development of the XQuery Update Facility, and should be
reviewed when critical decisions are made. These usage scenarios
should also prove useful in helping non-members of the XML Query
Working Group understand the intent and goals of the project.</p>
<dl>
<dt class="label">2.1 Updating persistent XML stores</dt>
<dd>
<p>Modify XML in persistent XML stores, including native XML
databases, XML files stored on a file system, or XML stored in SQL
databases.</p>
</dd>
<dt class="label">2.2 Modify XML messages</dt>
<dd>
<p>Modify XML messages to change status and add information created
while processing the message.</p>
</dd>
<dt class="label">2.3 Add to existing XML document</dt>
<dd>
<p>Add new data to an existing XML document; for instance, add a
new entry to a BLOG or a data log.</p>
</dd>
<dt class="label">2.4 Updating XML registries</dt>
<dd>
<p>Perform updates on configuration files, user profiles, or
administrative logs represented in XML.</p>
</dd>
<dt class="label">2.5 Creating edited copies</dt>
<dd>
<p>Create a new copy of an XML document or subtree that differs
from the original in the way specified by the update. For instance,
updates could be used to modify a web message in order to add new
information and change headers to reflect the modified status.</p>
</dd>
<dt class="label">2.6 Modifying XML views</dt>
<dd>
<p>Modifying XML views of non-XML sources, such as a <a href=
"#sqlxml">[SQL/XML]</a> view of a SQL database.</p>
</dd>
</dl>
</div>
<div class="div1">
<h2><a name="d3e236" id="d3e236"></a>3 Requirements</h2>
<div class="div2">
<h3><a name="d3e239" id="d3e239"></a>3.1 Terminology</h3>
<p>The following key words are used throughout the document to
specify the extent to which an item is a requirement for the work
of the XML Query Working Group:</p>
<dl>
<dt class="label"><a name="terminology-must" id=
"terminology-must"></a>MUST</dt>
<dd>
<p>This word means that the item is an absolute requirement.</p>
</dd>
<dt class="label"><a name="terminology-should" id=
"terminology-should"></a>SHOULD</dt>
<dd>
<p>This word means that there may exist valid reasons not to treat
this item as a requirement, but the full implications should be
understood and the case carefully weighed before discarding this
item.</p>
</dd>
<dt class="label"><a name="terminology-may" id=
"terminology-may"></a>MAY</dt>
<dd>
<p>This word means that an item deserves attention, but further
study is needed to determine whether the item should be treated as
a requirement.</p>
</dd>
</dl>
<p>When the words <a href="#terminology-must">MUST</a>, <a href=
"#terminology-should">SHOULD</a>, or <a href=
"#terminology-may">MAY</a> are used in this technical sense, they
occur as a hyperlink to these definitions. These words will also be
used with their conventional English meaning, in which case there
is no hyperlink. For instance, the phrase "the full implications
should be understood" uses the word "should" in its conventional
English sense, and therefore occurs without the hyperlink.</p>
</div>
<div class="div2">
<h3><a name="d3e274" id="d3e274"></a>3.2 General Requirements</h3>
<dl>
<dt class="label">3.2.1 Query Update Syntax</dt>
<dd>
<p>The syntax for updates <a href="#terminology-may">MAY</a> have
more than one syntax binding. One syntax <a href=
"#terminology-must">MUST</a> be convenient for humans to read and
write.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
<p>One syntax <a href="#terminology-must">MUST</a> be expressed in
XML in a way that reflects the underlying structure of the
operations.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.2.2 Declarativity</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be declarative. Notably, it <a href="#terminology-must">MUST</a> be
independent of any particular evaluation strategy.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.2.3 Protocol Independence</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be defined independently of any protocols with which it is
used.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.2.4 Error Conditions</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
define standard error conditions that can occur during the
execution of an update.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.2.5 Static Type Checking</dt>
<dd>
<p>The XQuery Update Facility <a href=
"#terminology-should">SHOULD</a> provide an optional static type
checking feature.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="d3e377" id="d3e377"></a>3.3 Relationship to XQuery
1.0</h3>
<dl>
<dt class="label">3.3.1 Based on Data Model</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be defined on the <a href="#xpath-datamodel">[XQuery 1.0 and XPath
2.0 Data Model]</a>.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
<div class="note">
<p class="prefix"><b>Note:</b></p>
<p>The properties of a Data Model instance that can be modified by
the XQuery Update Facility are discussed in <a href=
"#id-update-functionality"><b>3.4 XML Query Update
Functionality</b></a>.</p>
</div>
</dd>
<dt class="label">3.3.2 Based on XQuery</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be based on <a href="#xquery">[XQuery 1.0]</a>. The XQuery Update
Facility <a href="#terminology-must">MUST</a> use XQuery to
identify items to be updated. The XQuery Update Facility <a href=
"#terminology-must">MUST</a> use XQuery to specify items used in
the updates.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="id-update-functionality" id=
"id-update-functionality"></a>3.4 XML Query Update
Functionality</h3>
<dl>
<dt class="label">3.4.1 Locus of modifications</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to change the properties of existing nodes while preserving
their identity. The XQuery Update Facility <a href=
"#terminology-must">MUST</a> be able to create a new copy of a node
with a specific set of changes.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.2 Delete</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to delete nodes.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.3 Insert</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to insert new nodes in specified positions.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.4 Replace</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to replace a node.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.5 Changing values</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to change the value returned by the typed-value accessor
for a node.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.6 Modifying properties</dt>
<dd>
<p>The XQuery Update Facility <a href=
"#terminology-should">SHOULD</a> be able to modify some of the
properties of a node such as the name, type, content, nilled,
base-URI, etc.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been met.
The base-URI can not be modified.</p>
</dd>
<dt class="label">3.4.7 Moving nodes</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-may">MAY</a> be
able to move a node from one location to another.</p>
<p><img src="http://www.w3.org/Icons/red-ball.gif" alt=
"red status" /> <em>Status:</em> this requirement has not been met.
A node can be deleted, and a copy inserted in a new location, but
it will have a new identity. The Working Group felt that this
functionality would limit the environments in which the XQuery
Update Facility could be implemented.</p>
</dd>
<dt class="label">3.4.8 Conditional updates</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to do conditional updates.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.9 Iterative updates</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to iterate over nodes to do updates.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
</dd>
<dt class="label">3.4.10 Validation</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-may">MAY</a>
support an explicit XML Schema validation operation that preserves
node identity.</p>
<p><img src="http://www.w3.org/Icons/yellow-ball.gif" alt=
"yellow status" /> This requirement has not been met according to
its original formulation; however, the revalidation mode can be set
to ensure that type information is recovered and the resulting
document is valid according to the governing schema.</p>
<div class="note">
<p class="prefix"><b>Note:</b></p>
<p>The XQuery 1.0 validate expression creates a new copy of each
validated node, with a new identity. This requirement involves
preservation of identity.</p>
</div>
</dd>
<dt class="label">3.4.11 Compositionality</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
be able to compose update operators with other update
operators.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
<p>The XQuery Update Facility <a href="#terminology-may">MAY</a> be
compositional with respect to XQuery expressions; that is, it may
be possible to use an update wherever an XQuery expression is
used.</p>
<p><img src="http://www.w3.org/Icons/red-ball.gif" alt=
"red status" /> <em>Status:</em> this requirement has not been met
Updating expressions are limited to specific syntactic
contexts..</p>
</dd>
<dt class="label">3.4.12 Parameterization</dt>
<dd>
<p>The XQuery Update Facility <a href=
"#terminology-should">SHOULD</a> provide a means to parameterize
update operations.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been met.
Updating functions and external variables may both be used to
parameterize update operations.</p>
</dd>
</dl>
</div>
<div class="div2">
<h3><a name="d3e646" id="d3e646"></a>3.5 Transaction
characteristics</h3>
<p>In this section, the terms Atomicity, Consistency, Isolation,
and Durability are taken from the ACID model of transaction
characteristics for databases, which is described in <a href=
"#gray">[Transaction Processing Concepts and Techniques]</a>.</p>
<dl>
<dt class="label">3.5.1 Atomicity</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
provide a set of atomic operations, and <a href=
"#terminology-must">MUST</a> define a means to group atomic
operations into an atomic execution unit.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been met.
Multiple atomic operations can be done in a single query, which
constitutes the atomic execution unit.</p>
</dd>
<dt class="label">3.5.2 Consistency</dt>
<dd>
<p>At the end of an outermost update operation (that is, an update
operation invoked from the external environment), the data model
<a href="#terminology-must">MUST</a> be consistent with respect to
the constraints specified in the Data Model. In particular, all
type annotations <a href="#terminology-must">MUST</a> be consistent
with the content of the items they govern.</p>
<p><img src="http://www.w3.org/Icons/green-ball.gif" alt=
"green status" /> <em>Status:</em> this requirement has been
met.</p>
<p>The XQuery Update Facility <a href="#terminology-may">MAY</a>
define additional levels of granularity at which Data Model
constraints are enforced.</p>
<p><img src="http://www.w3.org/Icons/red-ball.gif" alt=
"red status" /> <em>Status:</em> this requirement has not been
met.</p>
</dd>
<dt class="label">3.5.3 Isolation</dt>
<dd>
<p>The XQuery Update Facility <a href=
"#terminology-should">SHOULD</a> define the means by which
operations can be isolated from concurrent operations.</p>
<p><img src="http://www.w3.org/Icons/yellow-ball.gif" alt=
"yellow status" /> The XQuery Update Facility defines operations
purely in terms of the XML Data Model. Propagation of XDM changes
to an underlying persistent store or other software system is
beyond the scope of this specification. This includes
isolation.</p>
</dd>
<dt class="label">3.5.4 Durability</dt>
<dd>
<p>The XQuery Update Facility <a href="#terminology-must">MUST</a>
define a means to control the durability of atomic operations and
atomic execution units.</p>
<p><img src="http://www.w3.org/Icons/yellow-ball.gif" alt=
"yellow status" /> The XQuery Update Facility defines operations
purely in terms of the XML Data Model. Propagation of XDM changes
to an underlying persistent store or other software system is
beyond the scope of this specification. This includes
durability.</p>
</dd>
</dl>
</div>
</div>
</div>
<div class="back">
<div class="div1">
<h2><a name="d3e735" id="d3e735"></a>A References</h2>
<dl>
<dt class="label"><span><a name="gray" id="gray"></a>Transaction
Processing Concepts and Techniques</span></dt>
<dd>
<div>Gray, J. and Reuter, A. 1994. <em>Transaction Processing
Concepts and Techniques</em>. Morgan Kaufmann Publishers, San
Mateo, CA</div>
</dd>
<dt class="label"><span><a name="sqlxml" id=
"sqlxml"></a>SQL/XML</span></dt>
<dd>
<div>International Organization for Standardization (ISO).
<em>ISO/IEC 9075-14:2008, Information Technology - Database
Languages - SQL - Part 14, XML-Related Specifications
(SQL/XML)</em>. (Available from American National Standards
Institute, New York, NY 10036, (212) 642-4900.)</div>
</dd>
<dt class="label"><span><a name="xpath-datamodel" id=
"xpath-datamodel"></a>XQuery 1.0 and XPath 2.0 Data
Model</span></dt>
<dd>
<div><a href="http://www.w3.org/TR/xpath-datamodel/"><cite>XQuery
1.0 and XPath 2.0 Data Model (XDM) (Second Edition)</cite></a>,
Norman Walsh, Mary Fernández, Ashok Malhotra, <em>et. al.</em>,
Editors. World Wide Web Consortium, 14 December 2010. This version
is http://www.w3.org/TR/2010/REC-xpath-datamodel-20101214/. The
<a href="http://www.w3.org/TR/xpath-datamodel/">latest version</a>
is available at http://www.w3.org/TR/xpath-datamodel/.</div>
</dd>
<dt class="label"><span><a name="xquery" id="xquery"></a>XQuery
1.0</span></dt>
<dd>
<div><a href="http://www.w3.org/TR/xquery/"><cite>XQuery 1.0: An
XML Query Language (Second Edition)</cite></a>, Don Chamberlin,
Anders Berglund, Scott Boag, <em>et. al.</em>, Editors. World Wide
Web Consortium, 14 December 2010. This version is
http://www.w3.org/TR/2010/REC-xquery-20101214/. The <a href=
"http://www.w3.org/TR/xquery/">latest version</a> is available at
http://www.w3.org/TR/xquery/.</div>
</dd>
</dl>
</div>
</div>
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