Models

A document model specifies the names of the elements that may be used in a document. It also dictates which elements have element content, mixed content and text content, and which elements are empty. When elements can contain other elements, restrictions on the content may include the names of the elements allowed, and even the order in which they may occur. The names of attributes each element may hold are given, and constraints may be placed on the possible value of an attribute.

The document modelling scheme provided by the standard is used to create a DTD (Document Type Definition). But a DTD is not a single object; this is the collective name for a model built from definitions in a number of markup declarations.

DTDs are typically ...

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