Comparing Schema Languages

This section compares schema languages to help you make decisions about implementing schemas into your XML applications.

Document Type Definitions (DTDs)

• DTDs specify content models for a set of XML documents.
• DTDs keep XML documents consistent.
• DTDs can be shared.
• DTDs provide a formal and complete definition of an XML vocabulary.
• DTDs are restricted to one DTD for each XML document.

Schemas

Like a DTD, a schema specifies the structure or model of a particular set of documents. Following are the benefits of using a schema language to describe XML document structure:

• Schemas use XML syntax.
• Schemas can be parsed by an XML parser.
• Schemas provide support for data types; the type of data contained in an element can be specified.
• Schemas allow global elements (elements that must be used the same way throughout the XML document) and local elements (elements that have a specific meaning in context).
• Schemas offer data type support (integer, string, Boolean), and the ability to create other data types.

Support for XDR schemas

The following products support XML-Data Reduced (XDR) schemas:

• Microsoft® BizTalk™ Server
• Microsoft SQL Server™ 2000
• Microsoft Office 2000
• Microsoft Internet Explorer version 5.0 and later

XDR schemas also have tools support in the following product:

• Extensibility's XML Authority

XSD Schemas

XML Schema definition language (XSD) schemas provide support for data types and for defining structures. This support allows you to create robust XML Schemas and validate XML instance documents against these schemas.

See Also

XDR Schema Developer's Guide