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XML Pocket Consultant by William R. Stanek

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Chapter 4. XML Elements in DTDs

Every element used in a valid document must be declared in the document’s document type definition (DTD). Element declarations specify the markup tags that can appear in a conforming document and how those tags can be used. If a DTD doesn’t declare elements that are used in a document, the document can’t be said to be valid.

Note

As you read this chapter, keep in mind that XML is case-sensitive. This means you must use the exact case for keywords and declarations specified. There are no exceptions.

Defining Elements in DTDs

Five types of elements are used in XML documents:

  • Those with standard content

  • Those with only character data

  • Those with mixed content

  • Those with any type of content allowed

  • Those with no content allowed ...

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