Document type definition (DTD) validation is implemented using the validity constraints defined in the World Wide Web Consortium (W3C) Extensible Markup Language (XML) 1.0 Recommendation.DTDs use a formal grammar to describe the structure and syntax of compliant XML documents; they specify content and values allowed for the XML document.Using XDK, you can write an application that includes a validating XML parser; that is, a program that parses and validates XML documents against a DTD.Depending on its implementation, a validating parser may: A validating XML parser tries to determine whether an instance document conforms to the rules of its associated XML schema. The piece of XML to validate is specified in the constructor.The constructors using more than a single argument are only relevant if you want to validate against a DTD and need to provide the location of the DTD itself - for details see the next section.
The Oracle XML Schema processor is a SAX-based XML schema validator that you can use to validate instance documents against an XML schema.
Document type definition (DTDs) were originally developed for SGML.
XML DTDs are a subset of those available in SGML and provide a mechanism for declaring constraints on XML markup.
Using XDK you can write a validating parser that performs this schema validation.
Depending on its implementation, a validating parser may: The processor must consider entity definitions and other constructs that are defined in a DTD that is included by the instance document.