Validation Overview

A schema defines the structure of XML documents. It provides details about the content model: which elements it contains and in what order, what its content can be, and which content these attributes can contain.

A schema verifies that the incoming XML documents are in the expected format.

An XML schema can be used to:

• Validate the content of an XML document.
• Determine whether the XML document is a valid instance of the vocabulary (grammar or rules) expressed by the XML schema.
• Describe the vocabulary for use by others creating XML documents.
• Define the elements that can appear within an XML document and the attributes that can be associated with an element.
• Define whether an element is empty or can include text.
• Define a default value for an attribute.
• Define elements that can contain child elements.
• Define the sequence for child elements that appear in an element.
• Define the number of child elements.

Writing validation rules

The following can be used to write validation rules.

• Document Type Definition (DTD)
• XML-Data Reduced (XDR) schema
• XML Schema definition language (XSD) schema

See Also

Frequently Asked Questions about Schemas | Comparing Schema Languages | DTD Developer's Guide | DTD Reference | XML Schema Elements