10.1 The XForms Namespace

The XForms namespace has the URI: http://www.w3.org/2001/06/xforms. Future revisions are expected to use a different identifier. This document uses the convention of an xform: prefix to represent elements and attributes that are part of the XForms Namespace.

XForms Processors must use the XML namespaces mechanism [XML Names] to recognize elements and attributes from this namespace. Except where specifically allowed by the Schema for XForms, foreign-namespaced elements are not allowed as content of elements in the XForms namespace. Foreign-namespaced attributes are, however, allowed on any XForms element. The XForms Processor must ignore any foreign-namespaced elements or attributes that are unrecognized.

10.2 XForms Elements

<xform
  xmlns = namespace-identifier
  id = xsd:ID
>
  <!-- Content: (submitInfo | bind)*, model, instance -->
</xform>

<xform xmlns="http://www.w3.org/2001/06/xforms" id="Person">
   <model xlink:href="Schema-Questionnaire.xform" />
   <instance xlink:href="URL-to-retrieve-defaults" /> 
   ...
</xform>

<model
  id = xsd:ID
  xlink:href = xsd:anyURI
>
  <!-- Content: ( schema subset syntax ) -->
</model>

<instance
  id = xsd:ID
  xlink:href = xsd:anyURI
>
  <!-- Content: (##other) -->
</instance>

<submitInfo
  id = xsd:ID
  xlink:href = xsd:anyURI
  method = xsd:string
>
  <!-- Content: (##empty) -->
</submitInfo>

<bind
  id = xsd:ID
  ref = XForms binding expression
>
  <!-- Content: (##empty) -->
</bind>

10.3 Integration with XLink

XForms make good use of XLink [XLink] features. To that end, the XLink namespace is integrated in the DTD/Schema, the majority of the attributes have sensible defaults, including those based on XLink roles defined below.

This document uses the convention of an xlink: prefix for the XLink namespace (informationally: as of this writing, the XLink namespace identifier is http://www.w3.org/1999/xlink - this may change when XLink reaches W3C Recommendation state. Please verify at [XLink])

Note that the XLink support uses a well-defined XLink failure mode: If an XLink attribute is not provided, the element looses its XLink specific meaning. We use this feature in order to allow application developers to either provide the model and instance via an external reference (via an xlink:href attribute) or to provide the data inline without the attribute. In the latter case, the XLink-specific meaning of the element is lost and the inline content used. If both inline content and external reference is provided, a processor must use the external reference and ignore the inline content.

For the purposes of XForms, we suggest that XLink aware processors switch from the xlink:type="locator" mode to the xlink:type="resource" mode. This should be specified in the document by setting xlink:type="resource", though a processing agent may not depend on it. In other words, the first two of the following examples must be treated identically:

<model>
  <!-- Content: ( schema subset syntax ) -->
</model>

<model xlink:type="resource">
  <!-- Content: ( schema subset syntax ) -->
</model>

<model xlink:href="URI" />

XLink as originally specified allows users to provide arc-type elements to specify traversal rules. The integration of arc-type elements in XForms would require additional elements in the xform element that are otherwise not necessary for XForms. Hence, for children of the xform element, the traversal rule is to traverse xlink:from the current document xlink:to the document pointed to by the external resource. The processor should behave as if xlink:actuate="onLoad" was specified. The xlink:show attribute is meaningless in this context, anyway.

An XForms processor is not required to implement full XLink--correct behavior of the xlink:href attribute (as defined above) is sufficient. It is permissible to construct the additional information from the semantics of the elements. An XForms Processor can not be XForms compliant, however, if it attempts to implement XLink and the implementation does not conform to XLink specification with respect to the attributes used by XForms.

The following definition of the XLink roles defines the relationship between the various resources participating in a XForms-based form, not properties that are inherent to the resources. It is perfectly permissible for the same resource to participate in various XForms-based forms in different roles.