2.2 Element Declarations

Element declarations in XSchemas are made using the ElementDecl element and its contents:

<!ELEMENT ElementDecl (Doc?, More?, Model, AttDef*)>
<!-- Name is the element name -->
<!ATTLIST ElementDecl
       id ID #IMPLIED
       prefix NMTOKEN #IMPLIED
       ns CDATA #IMPLIED
       Root (Recommended | Possible | Unlikely) "Possible">

The XSC:Name attribute identifies the name of the element, and is required. An element declaration would look like:

<XSC:ElementDecl Name="Species">

This declaration would declare an element named "Species", which would appear in an instance as:


The Name attribute must be unique within the set of elements, as it provides the name of the element as declared here, and is also used by other elements to refer to this element in their content model declarations. The Name attribute must also match the Name production in the XML 1.0 spec. (Effectively, this requires element names to begin with a letter, underscore, or colon.)

The id attribute, if it appears, must be unique within the document. This attribute may be used to uniquely identify this ElementDecl element for reference using XPointers and other tools. The prefix attribute identifies the prefix that will be applied to this elements and its attributes during conversion to DTDs, unless overridden in the attribute declaration itself. The ns attribute identifies the URI which functions as the namespace name for this element and its attributes. Namespace processing is covered further in Section 3.0, "XSchema and Namespaces".

The Root attribute provides authoring tools with a guide for which elements are likely root elements for documents. This is intended to simplify the choices presented to authors during document composition. Composition tools could use this to build a menu of likely starting points for a document. The Root attribute is purely a suggestion and does not require any action on the part of the processor.

Note that an element must declare a content model of some type, using the Model element, even if that content model is empty. Documentation (in the Doc element), non-XSchema extensions (in the More element) and attribute declarations (using AttDef elements) are optional.

Documentation about the element, additional extensions, content-model information, and attribute information are stored as sub-elements of the ElementDecl element. Documentation is covered in 2.6.1, Documentation Extensions. Additional extensions are covered in 2.6.2, Further Extensions. Content Models are covered in 2.3, Content Model Declarations, and attributes are covered in 2.4, Attribute Declarations.