XML Schema Complete Reference, The

E.4. XML DTDs and Schemas

document type declaration:

A declaration that may occur near the beginning of an XML document which prescribes the type name of the document element, sets up the information needed for the parser to handle the documents entity structure, and includes—directly or by reference—a DTD.

document type definition (DTD):

A part of an XML document contained in the document type declaration either directly or by reference, which provides a much weaker but similar capability in prescribing allowable types of attributes and elements at various points in the document.

Validity with respect to a DTD is defined by the XML Recommendation.

declaration:

1. A character string beginning with ‘<!’ and ending with ‘>’, typically making ...