Data Types

Unlike a Document Type Definition (DTD), XML Schema also allows the specification of a data type for an element or attribute. Data types specify the format of the data, provide for validation of the type by the XML parser, and enable data-type-specific processing in the XML Document Object Model (DOM).

Data type support includes primitive data types common to programming languages as well as the special attribute types specified in the XML Language Specification (for example, ID, IDREF, and NMTOKEN). A complete list of the data types can be found in the XML Data Types Reference. 

To make use of the data type support included with Internet Explorer 5, your XML Schema must include the datatypes namespace. The top-level "Schema" element declaration would look like this:

<Schema name="myschema"
        xmlns="urn:schemas-microsoft-com:xml-data"
        xmlns:dt="urn:schemas-microsoft-com:datatypes">
 <!-- ... -->
</Schema>

Within the "Schema" element, data types can be specified on an <ElementType> or <AttributeType> basis using one of two forms:

• dt:type attribute
• <datatype> element

Both forms are demonstrated below—the samples are equivalent.

<ElementType name="pages" dt:type="int"/>

<ElementType name="pages">
  <datatype dt:type="int" />
</ElementType>

The same applies to attributes. The <datatype> or dt:type attribute can be used directly on the <AttributeType>.

Note that although XML Schema support in Internet Explorer 5 allows data types to be specified within attributes, only the following data types are supported within attributes by the parser and DOM: string, id, idref, idrefs, nmtoken, nmtokens, entity, entities, enumeration, and notation. Support for the other data types will be added in a future release.