Special Edition Using XML, Second Edition

Internal Versus External DTD

Document Type Definitions can be incorporated into your XML documents in one of two ways: internally or externally.

As we've discussed in earlier chapters, the first line in your XML document should be the XML declaration

<?xml version="1.0" ?> 

Although this is not a formal requirement of XML, and XML is not required to contain this prolog, it is good form and a good authoring habit to always include it.

The next section that should follow the XML declaration, if you are authoring valid XML, is what is called the Document Type Declaration, and it takes the following form:

<!DOCTYPE name    SYSTEM uri> 

name and uri conform to the rules for naming and URIs. This Document Type Declaration is what is used to point to ...