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    <a href="http://www.w3.org/"><img src=
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    <h1><a name="title" id="title"></a>XPath Requirements
    Version 2.0</h1>

    <h2>W3C Working Draft 3 June 2005</h2>

    <dl>
      <dt>This version:</dt>

      <dd><a href="http://www.w3.org/TR/2005/WD-xpath20req-20050603/">http://www.w3.org/TR/2005/WD-xpath20req-20050603/</a></dd>

      <dt>Latest version:</dt>

      <dd><a href="http://www.w3.org/TR/xpath20req/">http://www.w3.org/TR/xpath20req/</a></dd>

      <dt>Previous versions:</dt>

      <dd><a href="http://www.w3.org/TR/2003/WD-xpath20req-20030822">http://www.w3.org/TR/2003/WD-xpath20req-20030822</a></dd>
      <dd><a href="http://www.w3.org/TR/2001/WD-xpath20req-20010214">http://www.w3.org/TR/2001/WD-xpath20req-20010214</a></dd>

      <dt>Editors:</dt>

      <dd>Mary Fernandez (AT&amp;T) <a href="mailto:mff@research.att.com">mff@research.att.com</a></dd>

      <dd>K Karun (Oracle) <a href="mailto:K.Karun@oracle.com">K.Karun@oracle.com</a></dd>

      <dd>Mark Scardina (Oracle) <a href="mailto:Mark.Scardina@oracle.com">Mark.Scardina@oracle.com</a></dd>

    </dl>

    <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2005 <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="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>, and
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    <hr title="Separator for header" />
  </div>

  <h2><a name="abstract" id="abstract">Abstract</a></h2>

  <p>This document describes the requirements for the XPath 2.0
  specification and is annotated with their resolution in <a href="#XPath2">[XPath 2.0]</a> or <a href="#XPathFO">[XQuery 1.0 and
  XPath 2.0 Functions and Operators]</a> and the <a href="#XQDM">[XQuery 1.0 and XPath 2.0 Data Model]</a>
  specifications.</p>

  <h2><a name="status" id="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. 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 includes, for each
requirement, a corresponding status, indicating the current situation
of the requirement in the XPath 2.0 family of specifications at the
time that they are being issued as Last Call Working Drafts in April, 2005.</p>

  <p>This is a W3C Working Draft for review by W3C Members and
  other interested parties. Publication as a Working Draft does not
  imply endorsement by the W3C Membership. This is a draft document
  and may be updated, replaced or obsoleted by other documents at
  any time. It is inappropriate to cite this document as other than
  work in progress.</p>

  <p>This document has been defined jointly by the <a href="http://www.w3.org/Style/XSL/">XSL Working Group</a> and the
  <a href="http://www.w3.org/XML/Query">XML Query Working Group</a>
  (both part of the <a href="http://www.w3.org/XML/Activity.html">XML Activity</a>).</p>

  <p>Comments on this document should be sent to the W3C mailing
  list <a href="mailto:public-qt-comments@w3.org">public-qt-comments@w3.org</a>
  (archived at <a href="http://lists.w3.org/Archives/Public/public-qt-comments/">http://lists.w3.org/Archives/Public/public-qt-comments/</a>).</p>

  <p>As of this publication, the Working Group expects to eventually
  publish this document as a Working Group Note. It is not expected to
  become a W3C Recommendation, and therefore it has no associated <a
  href="http://www.w3.org/Consortium/Patent-Policy-20040205">W3C
  Patent Policy licensing</a> obligations.</p>

  <p>A list of current W3C Recommendations and other technical
  documents can be found at <a href="http://www.w3.org/TR/">http://www.w3.org/TR/</a>.</p>

  <h2><a name="contents" id="contents">Table of contents</a></h2>1
  <a href="http://www.w3.org/TR/xpath20req#section-Goals">Goals</a><br />
  2 <a href="http://www.w3.org/TR/xpath20req#section-Requirements">Requirements</a><br />

  3 <a href="http://www.w3.org/TR/xpath20req#section-References">References</a><br />


  <h3><a name="appendices" id="appendices"></a>Appendices</h3>
  <hr />

  <h2><a name="section-Goals" id="section-Goals"></a>1 Goals</h2>

  <p>XPath 2.0 has the following goals:</p>

  <ul>
    <li>Simplify manipulation of XML Schema-typed content</li>

    <li>Simplify manipulation of string content</li>

    <li>Support related XML standards</li>

    <li>Improve ease of use</li>

    <li>Improve interoperability</li>

    <li>Improve i18n support</li>

    <li>Maintain backward compatibility</li>

    <li>Enable improved processor efficiency</li>
  </ul>

  <h2><a name="section-Requirements" id="section-Requirements"></a>2 Requirements</h2>

  <table summary="Presentation" border="0" cellspacing="0" width="100%">
    <tbody>
      <tr class="r1">
        <td class="item" align="right" valign="top"><b>1</b></td>

        <td colspan="3" class="item">
          <span class="req-must">Must&nbsp;Support the XML "Family"
          of Standards</span><br />

          <p>As part of the evolving family of XML standards, XPath
          2.0 MUST support the W3C XML architecture by integrating
          well with other standards in the family.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.1</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Express Data model in
          Terms of the Infoset</span><br />

          <p>XPath 2.0 data model MUST be expressed in terms of the
          <a href="#Infoset">XML Infoset</a>, including Post Schema
          Validation Infoset contributions. Ideally, XSLT, XPath,
          and XML Query should share a common data model.</p>

          <p class="satisfied">Satisfied by the <a href="http://www.w3.org/TR/xpath-datamodel/#intro">Introduction</a>
          section in <a href="#XQDM">[XQuery 1.0 and XPath 2.0 Data
          Model]</a>.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.2</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Provide Common Core
          Syntax and Semantics for XSLT 2.0 and XML Query
          1.0</span><br />

          <p>XSLT 2.0 contains an expression language which is
          "XPath 2.0 plus XSLT 2.0 extensions". XML Query 1.0
          contains an expression language which we believe should
          be "XPath 2.0 plus XML Query 1.0 extensions." The scope
          of XPath 2.0 must be the set of common functionality
          between the expression language of XSLT 2.0 and the
          expression language of XML Query 1.0. This will guarantee
          for Web developers and users that any common
          functionality are implemented with identical syntax and
          semantics.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-introduction">Introduction</a>
          in <a href="#XPath2">[XPath 2.0]</a>.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.3</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Support Explicit "For
          Any" or "For All" Comparison and Equality
          Semantics</span><br />

          <p>It MUST be possible for boolean expressions involving
          node-sets to explicitly use "for any" or "for all"
          semantics, otherwise known as explicit existential
          quantification and explicit universal quantification,
          respectively. Any <i>implicit</i> quantification should
          be explained in terms of these explicit semantics.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath20/#id-quantified-expressions">Quantified Expressions</a> in <a href="#XPath2">[XPath 2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>The following examples illustrate limitations
                  of XPath 1.0 that can be addressed by the
                  addition of existential and universal quantifiers
                  to XPath 2.0:</p>

                  <ol>
                    <li>In XPath 1.0, the expression <code>5 &gt;
                    $ns</code> evaluates to true if <code>5</code>
                    is greater than the <code>number()</code> value
                    of at least one node in the <code>$ns</code>
                    node set. There is no way to test whether
                    <code>5</code> is greater than the
                    <code>number()</code> values of all nodes in
                    <code>$ns</code>.</li>

                    <li>In XPath 1.0, the expression <code>$ns1
                    &gt; $ns2</code> evaluates to true if the
                    <code>number()</code> value of at least one
                    node in <code>$ns1</code> is greater than the
                    <code>number()</code> value of at least one
                    node in the <code>$ns2</code> node set. There
                    is no way to test whether the
                    <code>number()</code> values of all of the
                    nodes in <code>$ns1</code> are greater than all
                    the <code>number()</code> values of all nodes
                    in <code>$ns2</code>.</li>

                    <li>In XPath 1.0, the expression <code>5 =
                    $ns</code> evaluates to true if <code>5</code>
                    equals the <code>number()</code> value of at
                    least one node in the <code>$ns</code> node
                    set. There is no way to test whether
                    <code>5</code> equals the <code>number()</code>
                    value of all nodes in <code>$ns</code>.</li>

                    <li>In XPath 1.0, the expression <code>$ns1 =
                    $ns2</code> evaluates to true if the
                    <code>number()</code> value of at least one
                    node in <code>$ns1</code> equals the
                    <code>number()</code> value of at least one
                    node in the <code>$ns2</code> node set. There
                    is no way to test whether the
                    <code>number()</code> values of all of the
                    nodes in <code>$ns1</code> are greater than all
                    the <code>number()</code> values of all nodes
                    in <code>$ns2</code>.</li>

                    <li>In XPath 1.0, the expression <code>0 +
                    LineItem/@UnitPrice &gt; 40</code> is
                    equivalent to <code>0 +
                    number(OrderDetail/@UnitPrice) &gt; 40</code>
                    which will be true if the <i>first</i>
                    <code>LineItem</code> element's
                    <code>UnitPrice</code> attribute is greater
                    than 40. However, the expression
                    <code>LineItem/@UnitPrice &gt; 40</code> is
                    true if <i>any</i> of the <code>LineItem</code>
                    elements' <code>UnitPrice</code> attributes is
                    greater than 40. This difference in behavior
                    could be resolved through explicit
                    quantification.</li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.4</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Extend Set of
          Aggregation Functions</span><br />

          <p>XPath 1.0 currently supports <code>sum()</code> and
          <code>count()</code>. XSLT users have frequently
          requested the addition of <code>min()</code> and
          <code>max()</code>. XPath 2.0 MUST address this by
          extending its basic set of aggegration functions by
          adopting some or all of the ones defined for XML
          Query.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#aggregate.functions">Aggregate Functions</a> in <a href="#XPathFO">[XQuery 1.0 and XPath
          2.0 Functions and Operators]</a>.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.5</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Maintain Backwards
          Compatibility with XPath 1.0</span><br />

          <p>Any valid XPath 1.0 expression SHOULD also be a valid
          XPath 2.0 expression, and have the same semantics when
          operating in the absence of XML Schema type information.
          If not possible to achieve due to other requirements,
          XPath 2.0 should minimize the number of changes to the
          XPath 2.0 syntax to maximize backward compatibility with
          XPath 1.0.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-backwards-compatibility">Backwards Compatibility with XPath 1.0</a> in <a href="#XPath2">[XPath 2.0]</a>.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.6</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Provide Intersection
          and Difference Functions</span><br />

          <p>XPath 1.0 supports the union of two node sets. Set
          functionality in XPath 2.0 SHOULD be expanded to include
          intersection and difference functions, and should be
          compatible with equivalent functions supported by XML
          Query.</p>

          <p class="satisfied">Satisfied by <em>union</em>,
          <em>intersect</em>, and <em>except in</em> section
          <a href="http://www.w3.org/TR/xpath20/#combining_seq">
          Combining Node Sequences</a> in <a href="#XPath2">[XPath
          2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>
                      <p>Given an XML document like:</p>

                      <div class="java-class">
                        &lt;hr&gt;<br />
                        &nbsp;&nbsp; &lt;teams&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;team
                        id="t1"&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;members
                        ref="e101 e103"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;/team&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;team
                        id="t2"&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;members
                        ref="e102"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;/team&gt;<br />
                        &nbsp;&nbsp;&lt;/teams&gt;<br />
                        &nbsp;&nbsp;&lt;departments&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;department&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;employee
                        id="e101" name="Steve"
                        teams="t1"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;employee
                        id="e102" name="Jonathan"
                        teams="t2"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;employee
                        id="e103" name="James"
                        teams="t1"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;/department&gt;<br />

                        &nbsp;&nbsp;&lt;/departments&gt;<br />
                        &lt;/hr&gt;
                      </div><br />

                      <p>Format the list of employees that work in
                      the same department as the
                      <code>employee</code> with <code>id</code> =
                      <code>e101</code> and that are on the same
                      teams as that employee. To accomplish
                      this:</p>

                      <ul>
                        <li>
                          <p>Select the list of all employees in
                          the employee's department:</p>

                          <div class="java-class">
                            id('e101')/parent::department/employee
                          </div><br />
                        </li>

                        <li>
                          <p>Intersect that set with the list of
                          all employees who are members of the
                          current employee's teams:</p>

                          <div class="java-class">
                            id('e101')/id(id(@teams)/members/@ref)
                          </div><br />
                        </li>

                        <li>
                          <p>Difference that set with the list
                          containing the current employee so they
                          don't appear in their own list of team
                          members:</p>

                          <div class="java-class">
                            id('e101')
                          </div><br />
                        </li>
                      </ul>

                      <p>The result should be the employee
                      "James".</p>
                    </li>

                    <li>
                      <p>Given an XML document full of book
                      information, a book with multiple authors
                      appears like this:</p>

                      <div class="java-class">
                        &lt;books&gt;<br />
                        &nbsp;&nbsp;&lt;book&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;title&gt;Exciting
                        New Book&lt;/title&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;author&gt;Kay&lt;/author&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;author&gt;Muench&lt;/author&gt;<br />

                        &nbsp;&nbsp;&lt;/book&gt;<br />
                        &nbsp;&nbsp;&lt;book&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;title&gt;Building
                        Oracle XML Applications&lt;/title&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;author&gt;Muench&lt;/author&gt;<br />

                        &nbsp;&nbsp;&lt;/book&gt;<br />
                        &nbsp;&nbsp;&lt;book&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;title&gt;XSLT
                        Programmer's Reference&lt;/title&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;author&gt;Kay&lt;/author&gt;<br />

                        &nbsp;&nbsp;&lt;/book&gt;<br />
                        &lt;/books&gt;
                      </div><br />

                      <p>Assuming an XSLT key is defined as
                      follows:</p>

                      <div class="java-class">
                        &lt;xsl:key name="auth" match="book"
                        use="author"/&gt;
                      </div><br />

                      <p>then, to find the list of books that have
                      both Muench and Kay among their authors, you
                      need to select the intersection of
                      <code>key('auth','Muench')</code> and
                      <code>key('auth','Kay')</code>.</p>

                      <p>To find books authored by Muench but
                      <i>not</i> by Kay, you need to select the
                      difference of
                      <code>key('auth','Muench')</code> and
                      <code>key('auth','Kay')</code>.</p>
                    </li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>1.7</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Support Unary Plus
          Operator</span><br />

          <p>XML Schema allows decimals to have a leading plus. To
          align better with this, XPath 2.0 SHOULD allow this by
          providing a unary plus operator.</p>

          <blockquote>
            <p><b>Ed. Note:</b> There's a potential though rather
            remote problem if there are nodes in the source
            document containing a number with a leading plus sign.
            Currently the defined behavior is to convert these
            values to <code>NaN</code>, and this will change. A
            stylesheet that is looking for phone-numbers beginning
            with "+" might rely on this.</p>
          </blockquote>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#func-numeric-unary-plus">op:numeric-unary-plus</a> in <a href="#XPathFO">[XQuery 1.0 and XPath 2.0 Functions and Operators]</a>.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" align="right" valign="top"><b>2</b></td>

        <td colspan="3" class="item">
          <span class="req-must">Must&nbsp;Improve Ease of
          Use</span><br />

          <p>Users of XPath 1.0 have requested enhancements to
          simplify expression of common XPath use cases. XPath 2.0
          MUST address these frequently requested enhancements.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>2.1</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Loosen Restrictions on
          Location Steps</span><br />

          <p>To better align with <a href="#XPointer">XPointer</a>
          and to simplify the use of XPath expressions in which
          multiple alternatives are allowed for a given location
          step, XPath 2.0 MUST relax current restrictions for what
          can appear after a '<code>/</code>' in an XPath
          expression. Neither unions nor node-set functions are
          allowed to appear after a '<code>/</code>' in XPath
          1.0.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath20/#id-steps">Steps</a> which allow union and node-set functions in
          <a href="#XPath2">[XPath 2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>
                      <p>An XPointer's expression can use node-set
                      functions on the right of the
                      '<code>/</code>' in a path:</p>

                      <div class="java-class">
                        id("chap1")/range-to(id("chap2"))
                      </div><br />
                    </li>

                    <li>
                      <p>Allowing unions in a location step would
                      allow expressions like:</p>

                      <div class="java-class">
                        /foo/(xxx|yyy)/li/(p|eg)
                      </div><br />

                      <p>instead of the more cumbersome:</p>

                      <div class="java-class">
                        /foo/xxx/li/p&nbsp;&nbsp;|<br />
                        /foo/xxx/li/eg |<br />
                        /foo/yyy/li/p&nbsp;&nbsp;|<br />
                        /foo/yyy/li/eg
                      </div><br />
                    </li>

                    <li>
                      <p>Allowing node-set functions to appear in a
                      location step would allow expressions
                      like:</p>

                      <div class="java-class">
                        document("otherdoc.xml")/id("foo")/a/b
                      </div><br />

                      <p>and</p>

                      <div class="java-class">
                        document("otherdoc.xml")/key("x","foo")/a/b
                      </div><br />
                    </li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>2.2</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Provide a Conditional
          Expression</span><br />

          <p>Many users have requested the ability to return a
          conditional value based on a boolean expression. XPath
          2.0 MUST provide a conditional expression which takes
          three expressions:</p>

          <ol>
            <li><i>expression1 (boolean)</i></li>

            <li><i>expression2</i></li>

            <li><i>expression3</i></li>
          </ol>

          <p>and evaluates to <i>expression2</i> if
          <i>expression1</i> is <code>true</code> and to
          <i>expression3</i> if <code>expression1</code> is
          <code>false</code>. Only <i>expression1</i> and the
          expression to be returned must be evaluated.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath20/#id-conditionals">Conditional Expressions</a> in <a href="#XPath2">[XPath
          2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p><b>XSLT Use Cases</b></p>

                  <ol>
                    <li>In a template, construct a
                    <code>&lt;table&gt;</code> element with a
                    <code>border</code> attribute whose value is
                    provided by an <i>attribute value template</i>
                    and is conditional depending on the value of
                    the <code>frame</code> attribute of the current
                    node. If <code>@frame = 'none'</code>, then the
                    value of <code>border</code> should be
                    <code>0</code>, otherwise the value of
                    <code>border</code> should be
                    <code>1</code>.</li>

                    <li>Assign an XSLT variable a conditional value
                    based on whether the current node has any
                    <code>&lt;test&gt;</code> element children. If
                    it does, assign the value "<code>is</code>" to
                    the variable, otherwise assign the value
                    "<code>is not</code>".</li>

                    <li>
                      <p>Given a source XML document like this:</p>

                      <div class="java-class">
                        &lt;Emps&gt;<br />
                        &nbsp;&nbsp;&lt;Emp&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;
                        &lt;LastName&gt;Smith&lt;/LastName&gt;<br />

                        &nbsp;&nbsp;&lt;/Emp&gt;<br />
                        &nbsp;&nbsp;&lt;Emp&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&lt;CommonName&gt;Scott&lt;/CommonName&gt;<br />

                        &nbsp;&nbsp;&lt;/Emp&gt;<br />
                        &lt;/Emps&gt;
                      </div><br />

                      <p>provide an <code>&lt;xsl:sort&gt;</code>
                      select expression to sort the list of
                      employees on the value of their
                      <code>&lt;LastName&gt;</code> if it's
                      present, otherwise on the value of their
                      <code>&lt;CommonName&gt;</code> element.</p>
                    </li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>2.3</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Define Consistent
          Implicit Semantics for Collection-Valued
          Subexpressions</span><br />

          <p>In XPath 1.0, the use of a collection-valued
          subexpression can introduce an implicit existential
          quantification or choose-first-member operation into the
          containing expression's semantics. XPath 2.0 MUST define
          a consistent implicit semantics for expressions that have
          collection-valued subexpressions. This may require that
          XPath 2.0 expressions use explicit quantification or
          indexing expressions to achieve the same implicit
          semantics provided in XPath 1.0.</p>

          <p class="satisfied">Satisfied by inclusion of implicit
          existential quantification in <a href="http://www.w3.org/TR/xpath20/#id-general-comparisons">General Comparisons</a> in <a href="#XPath2">[XPath
          2.0]</a>. Note that it is not included in Value
          Comparisons. The first member semantics were dropped
          except for Backwards Compatibility mode.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>In XPath 1.0, the expression
                    <code>a[b=5]</code> returns
                    <code>&lt;a&gt;</code> elements that have ANY
                    <code>&lt;b&gt;</code> element child with value
                    5, where as the expression
                    <code>a[b+1=6]</code> returns
                    <code>&lt;a&gt;</code> elements whose FIRST
                    <code>&lt;b&gt;</code> element child has value
                    5. These results should be consistent for XPath
                    2.0.

                      <p class="satisfied">In 2.0 a[b+1=6] will
                      return an error if more than one b where in
                      1.0 it will ignore the other b's. This
                      produces a less surprising result for our
                      users.</p>
                    </li>

                    <li>Assume for this use case that the
                    typed-value of an element or attribute is
                    referenced using the syntax
                    <code>typed-value(elt)</code> and
                    <code>typed-value(@attr)</code>, respectively.
                    In XPath 2.0, when working with the typed value
                    of an element or attribute with
                    <code>boolean</code> type, the expression
                    <code>a[typed-value(b) = false()]</code> should
                    return <code>&lt;a&gt;</code> elements having
                    at least one <code>&lt;b&gt;</code> element
                    child with <code>boolean</code> value
                    <code>false</code>. Similarly, the expression
                    <code>a[typed-value(@b) = false()]</code>
                    should return &lt;a&gt; elements having a
                    boolean attribute <code>b</code> with value
                    <code>false</code>.</li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>2.4</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Support Additional
          String Functions</span><br />

          <p>Users of XSLT 1.0 have requested additional string
          manipulation functions. Common requests include string
          padding (with spaces, dashes, or other characters),
          string replacement, and converting strings to upper and
          lower case. XPath 2.0 SHOULD provide additional string
          functions. As with any string functions,
          internationalization issues need to be addressed to
          insure that the functionality is as broadly useful as
          possible.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top">
        <b>2.4.1</b></td>

        <td class="item">
          <span class="req-should">Should&nbsp;Simplify String
          Replacement</span><br />

          <p>XPath 1.0 provides the <code>translate()</code>
          function that allows each single character in a source
          string to be translated to another single character in
          the result string, or to be removed. Users of XPath 1.0
          frequently want to replace <i>sequences</i> of
          consecutive characters with other sequences of
          characters, which <code>translate()</code> does not
          support. XPath 2.0 SHOULD support a more flexible string
          replacement function.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#string.match">String Functions that Use Pattern Matching</a> in <a href="#XPathFO">[XQuery 1.0 and
          XPath 2.0 Functions and Operators]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>Replace each occurrence of "<code>foo</code>"
                  in a string with "<code>foobar</code>".</p>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top">
        <b>2.4.2</b></td>

        <td class="item">
          <span class="req-should">Should&nbsp;Simplify String
          Padding</span><br />

          <p>Often string values need to be padded on the left or
          right to make the value occupy a fixed length. XPath 2.0
          SHOULD support a string padding function that permits any
          character as a padding character.</p>
          
          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath-functions/#string-pad">eg:string-pad</a> in <a href="#XPathFO">[XQuery 1.0 and
          XPath 2.0 Functions and Operators]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>Pad the value of a string on the right to
                    ensure a length of 10 characters using
                    spaces</li>

                    <li>Pad the value of a string on the left to 10
                    characters using asterisks</li>

                    <li>Output a string containing as many dashes
                    as the length of a section title</li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top">
        <b>2.4.3</b></td>

        <td class="item">
          <span class="req-should">Should&nbsp;Simplify String Case
          Conversions</span><br />

          <p>XPath 2.0 SHOULD provide the ability to convert the
          case of text to upper or lower case for presentation
          and/or comparison.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#func-upper-case">fn:upper-case</a> and <a href="http://www.w3.org/TR/xpath-functions/#func-lower-case">fn:lower-case</a> in <a href="#XPathFO">[XQuery 1.0 and
          XPath 2.0 Functions and Operators]</a>.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>2.5</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Support Aggregation
          Functions Over Collection-Valued Expressions</span><br />

          <p>Users of XPath 1.0 frequently request the ability to
          apply an aggregate function, like <code>sum()</code>, to
          the values of expressions applied to a node set. XPath
          2.0 SHOULD support aggregation functions over expressions
          applied to node sets.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-for-expressions">For
          Expressions</a> in <a href="#XPath2">[XPath2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>
                      <p>Given a document like</p>

                      <div class="java-class">
                        &lt;sect title="Plan"&gt;<br />
                        &nbsp;&nbsp; &lt;sect
                        title="Overview"&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;sect
                        title="Competitors"&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;sect
                        title="SuperSoft"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;sect
                        title="BarnWare"/&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;/sect&gt;<br />

                        &nbsp;&nbsp; &lt;/sect&gt;<br />
                        &nbsp;&nbsp; &lt;sect
                        title="Details"&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;sect
                        title="Summary"/&gt;<br />
                        &nbsp;&nbsp; &lt;/sect&gt;<br />
                        &lt;/sect&gt;
                      </div><br />

                      <p>Calculate the maximum depth of the nesting
                      of <code>&lt;sect&gt;</code> elements. The
                      nodeset is identified by the expression
                      <code>//sect</code> and the expression to
                      maximize would be
                      <code>count(ancestor-or-self::sect)</code>.</p>
                    </li>

                    <li>Given the same document above, calculate
                    the average string length of section titles.
                    The nodeset is identified by
                    <code>//section/@title</code> and the
                    expression to sum would be
                    <code>string-length(.)</code>, divided by the
                    <code>count(//section/@title)</code></li>

                    <li>Given an XML document containing a purchase
                    order and its line <code>&lt;item&gt;</code>
                    elements, calculate the total amount of the
                    purchase order by summing the price times the
                    quantity of each item. The nodeset is
                    identified by <code>item</code>, and the
                    expression to sum would be <code>price *
                    quantity</code>.</li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" align="right" valign="top"><b>3</b></td>

        <td colspan="3" class="item">
          <span class="req-must">Must&nbsp;Support String Matching
          Using Regular Expressions</span><br />

          <p>Regular expressions provide a powerful way to specify
          string pattern matching and now play an important role in
          XML Schema as the mechanism by which pattern facets are
          specified. XPath 2.0 MUST support regular expressions for
          matching against strings using the regular expression
          notation established in <a href="#XSchemaData">XML
          Schema: Datatypes</a>.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#regex-syntax">Regular Expression Syntax</a> in <a href="#XPathFO">[XQuery 1.0 and XPath 2.0 Functions and
          Operators]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>
                      <p>Given XML like:</p>

                      <div class="java-class">
                        &lt;Data&gt;<br />
                        &nbsp;&nbsp;&lt;EmpRow&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp; :<br />
                        &nbsp;&nbsp;&lt;/EmpRow&gt;<br />
                        &nbsp;&nbsp;&lt;DeptRow&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;
                        &lt;Deptno&gt;10&lt;/Deptno&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;
                        &lt;Employees&gt;<br />
                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;EmpRow&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;Empno&gt;1000&lt;/Empno&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;Ename&gt;1000&lt;/Ename&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;/Emprow&gt;<br />

                        &nbsp;&nbsp;&nbsp;&nbsp;
                        &lt;/Employees&gt;<br />
                        &nbsp;&nbsp;&lt;/DeptRow&gt;<br />
                        &lt;/Data&gt;
                      </div><br />

                      <p>match elements that "end with
                      <code>Row</code> or <code>row</code>"</p>

                      <div class="java-class">
                        *[local-name() =~ ".*[rR]ow"]
                      </div><br />
                    </li>

                    <li>
                      <p>Match phone numbers like 123-456-7890</p>

                      <div class="java-class">
                        field[ . =~ "\d\d\d-\d\d\d\-\d\d\d\d"]
                      </div><br />
                    </li>

                    <li>
                      <p>Match any element name with the string
                      "Addr" contained within the name
                      (case-insensitively)</p>

                      <div class="java-class">
                        *[local-name() =~ ".*[Aa][Dd][Dd][Rr].*"]
                      </div><br />
                    </li>

                    <li>
                      <p>Match a string from a dynamic regular
                      expression</p>

                      <div class="java-class">
                        Department[Code =~
                        concat("[0-9][0-9]",$v,".*")]
                      </div><br />
                    </li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" align="right" valign="top"><b>4</b></td>

        <td colspan="3" class="item">
          <span class="req-must">Must&nbsp;Add Support for XML
          Schema Primitive Datatypes</span><br />

          <p><a href="#XSchemaData">[XML Schema: Datatypes]</a>
          defines a set of primitive datatypes. In addition to the
          types supported by the XPath 1.0 data model,
          <code>string</code>, <code>number</code>,
          <code>boolean</code>, and <code>node-set</code>, the
          XPath 2.0 data model MUST support XML Schema primitive
          types. XPath 2.0 will extend the XPath data model to
          accommodate working with elements and attribute values
          having an XML Schema primitive type.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.1</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Define the Operator
          Matrix and Conversions</span><br />

          <p>XPath 2.0 MUST support the operators and type-coercion
          rules defined by the joint XSLT/Schema/Query task force
          on operators.</p>

          <p class="satisfied">Satisfied by sections</p>

          <ul class="satisfied">
            <li><a href="http://www.w3.org/TR/xpath-functions/#numeric-functions">Functions and Operators on Numerics</a></li>

            <li><a href="http://www.w3.org/TR/xpath-functions/#d1e3606">Functions and Operators on Boolean Values</a></li>

            <li><a href="http://www.w3.org/TR/xpath-functions/#durations-dates-times">Functions and Operators on Durations, Dates and
            Times</a></li>

            <li><a href="http://www.w3.org/TR/xpath-functions/#QName-funcs">Functions Related to QNames</a></li>
          </ul>

          <p class="satisfied">in <a href="#XPathFO">[XQuery 1.0
          and XPath 2.0 Functions and Operators]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ul>
                    <li>
                      <p><b>General</b></p>

                      <ol>
                        <li>Use and create the type information of
                        any datatype</li>

                        <li>Do not require the user to respecify
                        the datatype (i.e. number and boolean)</li>

                        <li>Maintain the facet constraints of
                        primitive datatypes while manipulating the
                        value. For example, take a 14.4 number plus
                        a 14.4 number and return a 14.4
                        number.</li>
                      </ol>
                    </li>

                    <li>
                      <p><b>For DateTime</b></p>

                      <ol>
                        <li>Compare dates of documents and return a
                        boolean</li>

                        <li>Add a time or date interval and return
                        the same type</li>

                        <li>Add a scalar value to a time or date
                        and return the same type</li>

                        <li>
                          <p>Calculate an end time from a start
                          time+duration. For example, given:</p>

                          <div class="java-class">
                            &lt;appointment
                            time="20001224-16:00:00"
                            duration="1:00"/&gt;
                          </div>

                          <p>Produce the end-time:</p>

                          <div class="java-class">
                            End time: &lt;xsl:value-of
                            select="@time + @duration"/&gt;
                          </div><br />
                        </li>

                        <li>
                          <p>Detect intersections between datetime
                          durations</p>

                          <div class="java-class">
                            &lt;appointment
                            time="20001224-16:00:00"
                            duration="2:00" reminder="0:15"/&gt;
                          </div><br />

                          <div class="java-class">
                            &lt;appointment
                            time="20001224-17:00:00"
                            duration="1:00" reminder="0:15"/&gt;
                          </div><br />
                        </li>
                      </ol>
                    </li>

                    <li>
                      <p><b>For Boolean</b></p>

                      <p>Perform pattern matching on "yes" and
                      "no"</p>
                    </li>

                    <li>
                      <p><b>For QName</b></p>

                      <ol>
                        <li>Build a Namespace element from a
                        QName</li>

                        <li>Compare a Namespace URI from a QName
                        with a string</li>
                      </ol>
                    </li>
                  </ul>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.2</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Allow Scientific
          Notation for Numbers</span><br />

          <p>XML Schema specifies a lexical representation for
          doubles and floats that includes scientific notation as
          well as <code>INF</code>, <code>-INF</code> or
          <code>NaN</code>. XPath 2.0 MUST support the lexical
          representations of floats and doubles supported by XML
          Schema.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#d1e1156">Numeric Types</a> in <a href="#XPathFO">[XQuery 1.0 and XPath 2.0 Functions and
          Operators]</a>.</p>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.3</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Define Appropriate Cast
          and Constructor Functions</span><br />

          <p>XPath 2.0 MUST define an appropriate set of functions
          to allow users to cast and construct instances of XML
          Schema primitive types. At a minimum, this set MUST
          include cast and constructor functions for URI and
          date/time types.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-functions/#constructor-functions">Constructor Functions</a> and <a href="http://www.w3.org/TR/xpath-functions/#casting">Casting</a> in <a href="#XPathFO">[XQuery 1.0 and XPath
          2.0 Functions and Operators]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>Be able to compare an element or attribute
                  with an XML Schema date or time type with a
                  constant date or time value.</p>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.4</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Add List Data Type
          to the Type System of the Expression
          Langauge</span><br />

          <p>XML Schema allows the definition of simple types
          derived by list, including lists of unions of non-list
          simple types. XPath 2.0 SHOULD support an ordered list of
          simple-typed values.</p>

          <p class="satisfied">Satisfied by section <a href="http://www.w3.org/TR/xpath-datamodel/#sequences">Sequences</a> in <a href="#XQDM">[XQuery 1.0 and
          XPath 2.0 Data Model]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>Create an XSLT transformation that converts an
                  element structure like this:</p>

                  <div class="java-class">
                    &lt;xdr:attribute name="a1"
                    dt:type="enumeration" dt:values="a1 a2 a3"/&gt;
                  </div><br />

                  <p>into an alternative structure like this:</p>

                  <div class="java-class">
                    &lt;xsd:attribute name="a1"&gt;<br />
                    &nbsp;&nbsp;&lt;xsd:simpleType&gt;<br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&lt;xsd:restriction
                    base="NMTOKEN"&gt;<br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;xsd:enumeration
                    value="a1"/&gt;<br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;xsd:enumeration
                    value="a2"/&gt;<br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;xsd:enumeration
                    value="a3"/&gt;<br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&lt;/xsd:restriction&gt;<br />

                    &nbsp;&nbsp;&lt;/xsd:simpleType&gt;<br />
                    &lt;/xsd:attribute&gt;
                  </div><br />

                  <p>This requires the ability in XPath to select
                  the list of NMTOKENS values of the
                  <code>dt:values</code> attribute for
                  processing.</p>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.5</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Support Accessing
          Simple-Typed Value of Elements and
          Attributes</span><br />

          <p>The XPath 1.0 type system supports the
          <code>number</code>, <code>string</code>,
          <code>boolean</code>, and <code>node-set</code> types.
          <a href="#XSchemaData">XML Schema: Datatypes</a>
          introduces many new types. XPath 1.0 supports conversion
          of the simple-typed values of elements and attributes to
          strings. In addition to this functionality, XPath 2.0
          MUST support access to the native, simple-typed value of
          an element or attribute.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-typed-value">Typed Value and String Value</a>
          in <a href="#XPath2">[XPath 2.0]</a>.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>4.6</b></td>

        <td colspan="2" class="item">
          <span class="req-must">Must&nbsp;Define Behavior of
          Operators for Null Arguments</span><br />

          <p>Since the typed value of an element can be
          <code>null</code>, XPath 2.0 MUST define how the behavior
          of operations applies to null values.</p>

          <p class="satisfied">Satisfied by the Empty Sequence
          supported through the <a href="#XPath2">[XPath
          2.0]</a> language.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>Assuming the typed value of an element is
                  addressed using a syntax like
                  <code>typed-value(elementname)</code>, XPath
                  needs to specify what <code>1.20 *
                  typed-value(salary)</code> evaluates to when the
                  typed value of the <code>&lt;salary&gt;</code> is
                  <code>null</code>.</p>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" align="right" valign="top"><b>5</b></td>

        <td colspan="3" class="item">
          <span class="req-should">Should&nbsp;Add Support for XML
          Schema: Structures</span><br />

          <p><a href="#XSchemaStruc">XML Schema: Structures</a>
          enables users to define structured types and associate
          them to elements in a schema. XPath 2.0 SHOULD provide
          support for the common operations needed for navigation
          and selection of typed elements.</p>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>5.1</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Select
          Elements/Attributes Based on an Explicit XML Schema
          Type</span><br />

          <p>XML Schema : Structures provides the ability to define
          the type of an element or attribute. XPath 2.0 SHOULD be
          able to test whether an element or attribute is an
          instance of a given type.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-sequencetype-matching">SequenceType
          Matching</a> in <a href="#XPath2">[XPath 2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <ol>
                    <li>Select all elements that are instances of
                    the complex type <code>Address</code>.</li>

                    <li>Select all attributes that are instances of
                    the simple-type <code>xsd:integer</code>.</li>

                    <li>Select elements of type
                    <code>Address</code> indicated in the instance
                    with <code>xsi:type="Address"</code></li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>5.2</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Select
          Elements/Attributes Based on XML Schema Type
          Hierarchy</span><br />

          <p>XML Schema : Structures provides the ability to define
          a hierarchy of types by derivation. XPath 2.0 SHOULD be
          able to selects elements or attributes that are instances
          of a type, also matching any types derived from it by
          restriction or extension.</p>

          <blockquote>
            <p><b>Ed. Note:</b> This introduces some interesting
            precedence decisions about how matches for an explicit
            type would need to take precedence over matches for
            compatible types. In other words, given a template
            matching elements with types compatible to
            <code>Address</code> and another template explicitly
            matching type <code>USAddress</code>, one would expect
            the explicit type match to take precedence. Also
            consider the case where two templates exist, one that
            matches the <code>Address</code> type and one that
            matches the <code>USAddress</code> type. If an element
            of type RuralRouteAddress (further derived from
            USAddress) is considered for matching, one would expect
            the template for the "closest inherited ancestor", that
            is <code>USAddress</code>, to take precendence over a
            template matching the type of a "more distant inherited
            ancestor" like <code>Address</code>.</p>
          </blockquote>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-sequencetype-matching">SequenceType
          Matching</a> in <a href="#XPath2">[XPath 2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p><b>Derivation by Restriction</b></p>

                  <p>The <a href="#XSchemaPri">[XML Schema:
                  Primer]</a> defines the <code>Items</code> type
                  and the <code>ConfirmedItems</code> type which is
                  derived by restriction from <code>Items</code>.
                  Select purchase orders whose
                  <code>&lt;items&gt;</code> member element is an
                  instance of the <code>ConfirmedItems</code> type,
                  which restricts the minimum number of
                  <code>&lt;item&gt;</code> elements that can
                  appear to be at least one.</p>

                  <p><b>Derivation by Extension</b></p>

                  <p>The <a href="#XSchemaPri">[XML Schema:
                  Primer]</a> defines the <code>Address</code> type
                  and the <code>UKAddress</code> and
                  <code>USAddress</code> types which is derived by
                  extension from <code>Address</code>, adding
                  additional element content in the subtypes.</p>

                  <ol>
                    <li>Select all elements that are instances of
                    complex type <code>Address</code>, matching
                    elements of type <code>USAddress</code> and
                    elements of type <code>UKAddress</code> as
                    well.</li>

                    <li>Select all elements that are instances of
                    complex type <code>Address</code>, without
                    selecting elements of types derived from
                    <code>Address</code>.</li>

                    <li>Select all attributes that are instances of
                    the simple-type <code>xsd:integer</code>,
                    matching attribute of type
                    <code>SKU-Number</code> which derives from
                    <code>xsd:integer</code>.</li>
                  </ol>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r1">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>5.3</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Select Elements
          Based on XML Schema Substitution Groups</span><br />

          <p><a href="#XSchemaData">[XML Schema: Datatypes]</a>
          provides the ability to include two or more element names
          in a substitution group. XPath 2.0 SHOULD be able to test
          whether an element is a member of an XML Schema
          substitution group.</p>

          <p class="satisfied">Satisfied by <a href="http://www.w3.org/TR/xpath20/#id-sequencetype-matching">SequenceType
          Matching</a> in <a href="#XPath2">[XPath 2.0]</a>.</p>

          <table summary="Presentation" border="0">
            <tbody>
              <tr>
                <td><span class="title"><b>Use Case</b></span></td>
              </tr>

              <tr>
                <td>
                  <p>The <a href="#XSchemaPri">[XML Schema:
                  Primer]</a> defines the global
                  <code>&lt;ipo:comment&gt;</code> element as the
                  head of a substitution group, whose substitutible
                  member elements include
                  <code>&lt;ipo:customerComment&gt;</code> and
                  <code>&lt;ipo:shipComment&gt;</code>. Select the
                  list of all elements that are
                  <code>&lt;ipo:comment&gt;</code> elements,
                  including any elements that are substitutible for
                  <code>&lt;ipo:comment&gt;</code> through this
                  substitution group.</p>
                </td>
              </tr>
            </tbody>
          </table>
        </td>
      </tr>

      <tr class="r0">
        <td class="item" valign="top">
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>

        <td class="item" align="right" valign="top"><b>5.4</b></td>

        <td colspan="2" class="item">
          <span class="req-should">Should&nbsp;Support Lookups
          Based on Schema Unique Constraints and Keys</span><br />

          <p><a href="#XSchemaData">[XML Schema: Datatypes]</a>
          supports named, multi-part keys. XPath 2.0 SHOULD support
          a mechanism for looking up the element to which a Schema
          key refers. Similar mechanisms already exist, such as the
          <code>id()</code> function in XPath 1.0 and the
          <code>key()</code> function in XSLT.</p>

          <p class="notsatisfied">Not Satisfied due to lack of use
          cases and existing functionality in host languages to
          create keys.</p>
        </td>
      </tr>
    </tbody>
  </table>

  <div class="div2">
    <h2><a name="section-References" id="section-References"></a>3
    References</h2>

    <dl>
      <dt class="label"><a id="XQDM" name="XQDM"></a>XQuery 1.0 and
      XPath 2.0 Data Model</dt>

      <dd>World-Wide Web Consortium <em>XQuery 1.0 and XPath 2.0
      Data Model</em>. See <a href="http://www.w3.org/TR/xpath-datamodel/">http://www.w3.org/TR/xpath-datamodel/</a></dd>

      <dt class="label"><a id="XPath" name="XPath"></a>XPath
      1.0</dt>

      <dd>World-Wide Web Consortium <em>XML Path Language
      (XPath)</em>: Version 1.0. November, 1999. See <a href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a>.</dd>

      <dt class="label"><a id="XPathReq" name="XPathReq"></a>XPath
      Requirements Version 2.0</dt>

      <dd>World Wide Web Consortium, <em>XPath Requirements Version
      2.0</em>. See <a href="http://www.w3.org/TR/xpath20req">http://www.w3.org/TR/xpath20req</a>.</dd>

      <dt class="label"><a id="XPath2" name="XPath2"></a>XPath
      2.0</dt>

      <dd>World-Wide Web Consortium <em>XML Path Language
      (XPath)</em>: Version 2.0. See <a href="http://www.w3.org/TR/xpath20/">http://www.w3.org/TR/xpath20/</a>.</dd>

      <dt class="label"><a id="XSLT2" name="XSLT2"></a>XSLT
      2.0</dt>

      <dd>World Wide Web Consortium, <em>XSL Transformations
      Language (XSLT)</em>: Version 2.0. See <a href="http://www.w3.org/TR/xslt20/">http://www.w3.org/TR/xslt20/</a>.</dd>

      <dt class="label"><a id="XQWG" name="XQWG"></a>XML Query
      Working Group</dt>

      <dd>World Wide Web Consortium, <em>XML Query Working
      Group</em>. Home page: <a href="http://www.w3.org/XML/Query">http://www.w3.org/XML/Query</a>.</dd>

      <dt class="label"><a id="XSLWG" name="XSLWG"></a>XSL Working
      Group</dt>

      <dd>World Wide Web Consortium, <em>XSL Working Group</em>.
      Home page: <a href="http://www.w3.org/Style/XSL/">http://www.w3.org/Style/XSL/</a>.</dd>

      <dt class="label"><a id="XQuery" name="XQuery"></a>XQuery
      1.0: A Query Language for XML</dt>

      <dd>World Wide Web Consortium, <em>XQuery 1.0: A Query
      Language for XML</em>. See <a href="http://www.w3.org/TR/xquery/">http://www.w3.org/TR/xquery/</a>.</dd>

      <dt class="label"><a id="XQueryReq" name="XQueryReq"></a>XML
      Query Requirements</dt>

      <dd>World Wide Web Consortium, <em>XML Query
      Requirements</em>. See <a href="http://www.w3.org/TR/2005/WD-xquery-requirements-20050603/">http://www.w3.org/TR/2005/WD-xquery-requirements-20050603/</a>.</dd>

      <dt class="label"><a id="XPointer" name="XPointer"></a>XPointer</dt>

      <dd>World Wide Web Consortium, <em>XPointer xpointer()
      Scheme</em>. See <a href="http://www.w3.org/TR/xptr-xpointer/">http://www.w3.org/TR/xptr-xpointer/</a>.</dd>

      <dt class="label"><a id="XSchemaPri" name="XSchemaPri"></a>XML Schema: Primer</dt>

      <dd>World Wide Web Consortium, <em>XML Schema Part 0:
      Primer</em>. See <a href="http://www.w3.org/TR/xmlschema-0/">http://www.w3.org/TR/xmlschema-0/</a>.</dd>

      <dt class="label"><a id="XSchemaStruc" name="XSchemaStruc"></a>XML Schema: Structures</dt>

      <dd>World Wide Web Consortium, <em>XML Schema Part 1:
      Structures</em>. See <a href="http://www.w3.org/TR/xmlschema-1/">http://www.w3.org/TR/xmlschema-1/</a>.</dd>

      <dt class="label"><a id="XSchemaData" name="XSchemaData"></a>XML Schema: Datatypes</dt>

      <dd>World Wide Web Consortium, <em>XML Schema Part 2:
      Datatypes</em>. See <a href="http://www.w3.org/TR/xmlschema-2/">http://www.w3.org/TR/xmlschema-2/</a>.</dd>

      <dt><a id="Infoset" name="Infoset"></a>XML Information
      Set</dt>

      <dd>World Wide Web Consortium, <em>XML Information Set</em>.
      See <a href="http://www.w3.org/TR/xml-infoset/">http://www.w3.org/TR/xml-infoset/</a>.</dd>

      <dt><a id="XPathFO" name="XPathFO"></a>XQuery 1.0 and XSLT
      2.0 Functions and Operators</dt>

      <dd>World Wide Web Consortium, <em>XQuery 1.0 and XSLT 2.0
      Functions and Operators</em>. See <a href="http://www.w3.org/TR/xpath-functions/">http://www.w3.org/TR/xpath-functions/</a>.</dd>

      <dt>&nbsp;</dt>

      <dt>&nbsp;</dt>

      <dt><a href="http://www.w3.org/TR/xptr-xpointer/"></a></dt>
    </dl>
  </div>
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