4 Document Structure

The XForms specification is an application of XML [XML 1.0], and has been designed for use within other XML vocabularies, in particular XHTML [XHTML 1.0]. This chapter discusses the structure and high-level features of XForms that allow this specification to be used with other document types.

4.1 The XForms Namespace

The XForms namespace has the URI: http://www.w3.org/2001/12/xforms. Any future Working Drafts are expected to use a different identifier, though a final identifier will be allocated before XForms becomes a W3C Recommendation.

XForms Processors must use the XML namespaces mechanism [XML Names] to recognize elements and attributes from this namespace.

4.2 Horizontally Applicable Markup

For cases when a particular element needs to be referred to from another context, every element in the XForms namespace has declared an attribute id of type xsd:ID in the Schema for XForms.

Foreign-namespaced attributes are allowed on any XForms element. The XForms Processor must ignore any foreign-namespaced elements or attributes that are unrecognized.

Except where specifically allowed by the Schema for XForms, foreign-namespaced elements are not allowed as content of elements in the XForms namespace.

4.3 XForms Head Elements

4.3.1 model

Element model is used as a container for other XForms elements, embedded in the head section of other document types such as XHTML. A single containing document may contain any number of model elements.

Example: XML Representation: <model>
  id = xsd:ID
  <!-- Content: instance?, schema?, (privacy|submitInfo|bind|action|extension)* -->

id = xsd:ID - Optional unique identifier used to refer to this particular model element.

For example:

<model xmlns="http://www.w3.org/2001/12/xforms" id="Person">
   <instance xlink:href="http://example.com/cgi-bin/get-instance" /> 
   <schema xlink:href="Schema-Questionnaire.xsd" />

4.3.2 instance

Element instance is used to define initial instance data. The instance data may be defined inline or obtained from a external URI.

Example: XML Representation: <instance>
  xlink:href = xsd:anyURI
  <!-- Content: (##other) -->

xlink:href = xsd:anyURI - Optional link to externally defined instance data

The content of the instance element is arbitrary XML in any namespace other than the XForms namespace. Authors must ensure that proper namespace declarations are used for content within the instance element.

4.3.3 schema

Element schema is used to define the schema portion of the XForms Model. The schema information may be defined inline or obtained from an external URI.

Example: XML Representation: <schema>
  xlink:href = xsd:anyURI
  <!-- Content: ##other (though typically <xsd:schema>) -->

xlink:href = xsd:anyURI - Optional link to an externally defined XForms Model.

4.3.4 submitInfo

Element submitInfo provides information on how, where and what to submit .

Example: XML Representation: <submitInfo>
  (single node binding attributes)
  action = xsd:anyURI
  mediaTypeExtension = "none" | qname-but-not-ncname : "none"
  method = "post" | "get" | qname-but-not-ncname : "post"
  version = xsd:NMTOKEN
  indent = xsd:boolean
  encoding = xsd:string
  mediaType = xsd:string
  omitXMLDeclaration = xsd:boolean
  standalone = xsd:boolean
  CDATASectionElements = list of xsd:QName
  replace = "all" | "instance" | "none" | qname-but-not-ncname : "all"
  <!-- Content: (##empty) -->

single node binding attributes - optional selector enabling submission of a portion of the instance data
action - Required destination for submitted instance data.
mediaTypeExtension - Optional information, additional to the mediaType, describing the serialization format.
method - Optional indicator as to the protocol to be used to deliver the serialized instance data.
version - corresponds to the version attribute of xsl:output
indent - corresponds to the indent attribute of xsl:output
encoding - corresponds to the encoding attribute of xsl:output
mediaType - corresponds to the media-type attribute of xsl:output
omitXMLDeclaration - corresponds to the omit-xml-declaration attribute of xsl:output
standalone - corresponds to the standalone attribute of xsl:output
CDATASectionElements - corresponds to the cdata-section-elements attribute of xsl:output
replace - specifier for how the information returned after submit should be applied.


Many of these attributes correspond to XSLT attributes [XSLT]. Note that the XSLT attributes doctype-system and doctype-public are not supported in XForms processing.


Note also that attribute mediaTypeExtension is useful in cases where a media type alone is not sufficiently precise. For instance, a SOAP envelope would not be adequately described simply by "text/xml", additional information would be required.

4.3.5 bind

Element bind is defined at 6 Constraints.

4.3.6 privacy

Element privacy is used to associate a P3P [P3P 1.0] policy reference with a particular form.

Example: XML Representation: <privacy>
  xlink:href = xsd:anyURI
  <!-- Content: (##empty) -->

xlink:href = xsd:anyURI - Optional link to an externally defined P3P policyref file (not an actual policy).

4.3.7 action

Defined at 9.16 action.

4.3.8 extension

Defined at extension.

4.4 XForms and XLink

XForms use XLink [XLink] features for linking, or defining an explicit relationship between resources (or portions of resources), which may be either local or remote.

To that end, the XForms schema references the XLink namespace with sensible defaults.Other than xlink:href attributes, form authors in most cases will not be required to explicitly write XLink-specific elements or attributes.

All XLinks in XForms are simple links. For further details, see 4.4.1 XLink Conformance and Examples.

4.4.1 XLink Conformance and Examples

An XForms processor is not required to implement full XLink—correct behavior of the xlink:href attribute (as defined in this chapter) is sufficient. For example, an XForms Processor must accept and correctly process the schema in both of the following:

Example: External schema constraints
  <xforms:schema xlink:href="URI-to-remote-schema.xsd" />
Example: Inline schema constraints
    <xsd:schema ...>
      <!-- Content: ... -->

This second example is unusual in that the xforms:schema element defaults an attribute xlink:type="simple" but lacks an xlink:href attribute to make the link meaningful. In this situation, the XForms Processor should switch from simple mode to none mode for the element lacking attribute xlink:href. For compatibility with XLink, the second example should be explicitly authored as follows:

Example: Inline schema constraints, with explicit xlink:type
  <xforms:schema xlink:type="none">
      <!-- Content: ... -->

Manual override of the xlink:type attribute.

If both inline content and external reference is provided, a processor must use the external reference and ignore the inline content.