To ensure validity in your XML documents, learn how to use DTDs, which provide a roadmap for describing and documenting the structure.Topics include DTD examples, structure of a DTD, drawbacks, and alternatives.

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All the applications that referenced the DTD would automatically use the new, updated structure.

A DTD can be internal, residing within the body of a single XML document.

XML documents may be parsed and validated before they are ever loaded by an application.

That way, XML data that is not valid can be flagged as "invalid" before it ever gets processed by the application (thus saving a lot of the headaches that corrupt or incomplete data can cause).

Although validation is optional, if an XML author is publishing an XML document for which maintaining the structure is vital, the author can reference a DTD from the XML document and use a validating XML parser during processing.

Requiring that an XML document be validated against a DTD ensures the integrity of the data structure.

The DTD includes element definitions, entity definitions, and parameters.

Finally, before closing the chapter, we will explore some of the drawbacks of DTDS and emerging alternatives for validation.

A DTD provides a roadmap for describing and documenting the structure that makes up an XML document.

A DTD can be used to determine the validity of an XML document.

This type of assurance for XML document structure is vital for e-commerce applications and business-to-business processing, among other things.