This tutorial has taught you how to describe the structure of an XML document.
You have learned how to use a DTD to define the legal elements of an XML document, and how a DTD can be declared inside your XML document, or as an external reference.
You have learned how to declare the legal elements, attributes, entities, and CDATA sections for XML documents.
You have also seen how to validate an XML document against a DTD.
The next step is to learn about XML Schema.
XML Schema is used to define the legal elements of an XML document, just like a DTD. We think that very soon XML Schemas will be used in most Web applications as a replacement for DTDs.
XML Schema is an XML-based alternative to DTD.
Unlike DTD, XML Schemas has support for data types and namespaces.
If you want to learn more about XML Schema, please visit our XML Schema tutorial.