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<h1>XForms And XPath</h1>
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<p class="intro">XForms uses XPath to address data. This is called binding.</p>
<hr />
<h2>XForms Binding</h2>
<p>XForms uses two sections to define data: The XForms model and the XForms user
interface.</p>
<p>The XForms model is an XML template (instance) for the data, and the XForms
user interface is a description of the input and display of the data.</p>
<p>XForms uses <b>XPath</b> to define the connection between the two sections.
This is called <b>binding</b>.</p>
<hr />
<h2>XPath</h2>
<p>XPath is a W3C standard syntax for defining parts of XML documents.</p>
<p>XPath uses path expressions to identify nodes in an XML document. These path
expressions look much like the expressions you see when you work with a
computer file system.</p>
<p>This XPath expression:</p>
<table class="ex" width="100%" cellpadding="2" cellspacing="0" border="1">
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<pre>/person/fname</pre>
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<p>addresses the fname node in the XML document:</p>
<table class="ex" cellpadding="2" cellspacing="0" width="100%" border="1">
<tr>
<td>
<pre><person>
<fname>Hege</fname>
<lname>Refsnes</lname>
</person></pre>
</td>
</tr>
</table>
<p><a href="../xpath/default.asp">Learn more about XPath in our XPath tutorial</a></p>
<hr />
<h2>Binding Using Ref</h2>
<p>With an XForms model instance like this:</p>
<table class="ex" width="100%" cellpadding="2" cellspacing="0" border="1">
<tr>
<td>
<pre><instance>
<person>
<name>
<b><fname/></b>
<b><lname/></b>
</name>
</person>
</instance></pre>
</td>
</tr>
</table>
<p>The XForms user interface can <b>bind</b> <input> elements using the <b>ref
attribute</b>:</p>
<table class="ex" width="100%" cellpadding="2" cellspacing="0" border="1">
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<td>
<pre><input ref=<b>"name/fname"</b>>
<label>First Name</label>
</input></pre>
<pre><input ref=<b>"name/lname"</b>>
<label>Last Name</label>
</input></pre>
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<p>The ref="name/fname" attribute in the example above is an XPath expression
pointing to the <fname> element in the instance model. This <b>binds</b>
the input field to the <fname>
element in the XML document (instance) that is collecting data from the form.</p>
<p>The XForms user interface could also use a reference like this:</p>
<table class="ex" width="100%" cellpadding="2" cellspacing="0" border="1">
<tr>
<td>
<pre><input ref=<b>"/person/name/fname"</b>>
<label>First Name</label>
</input></pre>
<pre><input ref=<b>"/person/name/lname"</b>>
<label>Last Name</label>
</input></pre>
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<p>In the example above, the slash (/) at the beginning of the XPath expression
indicates the root of the XML document. </p>
<hr />
<h2>Binding Using Bind</h2>
<p>With an XForms model instance like this:</p>
<table class="ex" width="100%" cellpadding="2" cellspacing="0" border="1">
<tr>
<td>
<pre><model>
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