XForms does not specify normatively where XForms controls and models must be placed within an HTML document. The convention is to place <xforms:model> elements within <xhtml:head>, and controls within <xhtml:body>. Orbeon Forms is more flexible on this:

• <xforms:model> can be placed within <xhtml:head> as is usual, but also under <xhtml:body> and even nested within other XForms elements. For example:

  <xxforms:dialog id="my-dialog" model="my-dialog-model">
  <xforms:label>My Dialog</xforms:label>
  <xforms:group> ... </xforms:group>
  <xforms:model id="my-dialog-model">
    <!-- Model used by the dialog <-->
    ...
  </xforms:model>
</xxforms:dialog>

  In this particular case, this allows you to write your dialog as a module in a completely separate file and to XInclude that file within your main form.

  At the moment, nested models behave exactly as if they were placed under <xhtml:head>. It is just a syntactic convenience to be able to place them within elements such as <xxforms:dialog>.

• Attribute Value Templates (AVTs) can be placed on HTML elements outside <xhtml:body>.

  <xhtml:body lang="{instance('language')}">
  ...
</xhtml:body>

• A single <xforms:output> control may be placed within <xhtml:title>. This allows dynamically changing the HTML document title using XForms.

  <xhtml:title>
  <xforms:output value="instance('resources')/title"/>
</xhtml:title>

NOTE: Even though AVTs and <xforms:output> elements may be placed before any XForms model, they are still considered part of the XForms "view" of the XForms document and refer to data placed in models.

• XPath focus points to a node in instance i2 in model m2
• form author specifies model="m1"
• but statically, the context model is already m1 because that is the default
• therefore the implementation does not restore the XPath focus to the root element of i1 in model m1
• the XPath focus remains that of the enclosing group, which is the root element of instance i2 in model m2
• xf:output displays "I am i2"

• XPath focus points to a node in instance i2 in model m2
• form author specifies model="m1"
• implementation, at runtime, compares the two models and sees that they are different
• implementation therefore restores the XPath focus to the root element of i1 in model m1
• xf:output displays "I am i1"

In XForms, <label>, <hint>, <help> and <alert> ("LHHA") elements must always be nested within a control. In HTML on the other hand, the <label> element supports a for attribute which relates the element to a control. Orbeon Forms follows HTML and support the for attribute on all the LHHA elements. This allows placing LHHA elements in other locations on the page:

<table>
  <tr>
    <td>
      <xforms:label for="first-name-control">Please enter your first name:</xforms:label>
    </td>
    <td>
      <xforms:input id="first-name-control" ref="first-name" />
    </td>
    <td>
      <xforms:hint for="first-name-control">Just your first name...</xforms:hint>
    </td>
  </tr>
</table>
<p>
  <xforms:alert for="first-name-control">Oops the first name is not valid</xforms:alert>
</p>

NOTE: Standalone LHHA elements must not cross <xforms:repeat> boundaries.

Orbeon Forms supports the exforms:iterate attribute, also available as xxforms:iterate attribute, on XForms action elements. Consider the following instances:

<xforms:instance id="main-instance">
  <instance xmlns=""/>
</xforms:instance>

<xforms:instance id="template-instance">
  <book xmlns="">
    <title/>
    <author/>
  </book>
</xforms:instance>

<xforms:instance id="source-instance">
  <instance xmlns="">
    <title>Don Quixote de la Mancha</title>
    <author>Miguel de Cervantes Saavedra</author>
    <title>Jacques le fataliste et son maître</title>
    <author>Denis Diderot</author>
    <title>Childhood's End</title>
    <author>Arthur C. Clarke</author>
  </instance>
</xforms:instance>

The following action iterates over the <title> elements of source-instance. For each of those, a new <book> element, copied from the template stored in template-instance, is inserted into main-instance. Then values from the <title> and <author> elements are copied over to the new structure. The XForms 1.1 context() function provides access to each of the iterated nodes:

<xforms:action ev:event="xforms-ready"
    xxforms:iterate="instance('source-instance')/title">
  <xforms:insert context="instance('main-instance')" nodeset="book"
       origin="instance('template-instance')"/>
  <xforms:setvalue ref="instance('main-instance')/book[last()]/title"
       value="context()"/>
  <xforms:setvalue ref="instance('main-instance')/book[last()]/author"
       value="context()/following-sibling::author"/>
</xforms:action>

The resulting main-instance is as follows:

<instance>
  <book>
    <title>Don Quixote de la Mancha</title>
    <author>Miguel de Cervantes Saavedra</author>
  </book>
  <book>
    <title>Jacques le fataliste et son maître</title>
    <author>Denis Diderot</author>
  </book>
  <book>
    <title>Childhood's End</title>
    <author>Arthur C. Clarke</author>
  </book>
</instance>

NOTE: Because Orbeon Forms uses XPath 2.0, xxforms:iterate is not limited to returning node-sets, but can return sequences of items such as strings.

For more information about eXforms extensions, please visit the eXforms site.

XForms 1.1 introduces the context attribute on <xforms:insert> and <xforms:delete>. Orbeon Forms supports this convenient attribute on all XForms elements changing the XPath evaluation context, including controls, actions, binds, and submissions.

The context attribute overrides the in-scope XPath evaluation context for an action. It applies before the ref and context attributes, but after the model attribute.

One convenient use is to just change the context within a group:

<xforms:group context="personal-information">
   ...
</xforms:group>

NOTE: It is also possible to use ref in this case, but doing so has the side effect of binding the group to an instance data node, which may affect group relevance, for example.

<xforms:select1> supports an extension attribute called xxforms:group which allows grouping a series of radio buttons together in a way similar to the name attribute in HTML.

In general, this attribute is not necessary. It is useful in the following case:

• Multiple <xforms:select1 appearance="full"> point to the same node.

• You enable deferred event handling on the client.

The xxforms:group attribute must contain an identifier unique between groups of radio controls. Example:

<xforms:repeat nodeset="instance('countries')/country">
  <xxforms:variable name="country" select="."/>
  <xhtml:tr>
    <xhtml:td>
      <xforms:select1 appearance="full" ref="instance('selected')"
                      xxforms:group="country-code-group">
        <xforms:item>
          <xforms:label/>
          <xforms:value value="$country/us-code"/>
        </xforms:item>
      </xforms:select1>
    </xhtml:td>
  </xhtml:tr>
</xforms:repeat>

NOTE: This attribute does not work in noscript mode yet even though it would be very useful in this case as well.