Section 15.2. Prolog vs. instance

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15.2. Prolog vs. instance

Most document representations start with a header that contains information about the actual document and how to interpret its representation. This is followed by the representation of the real document.

For instance, HTML has a HEAD element that can contain the TITLE and META elements. After the HEAD element comes the BODY. This is where the representation of the actual document resides. Similarly, email messages have "header lines" that describe who the message came from, to whom it is addressed, how it is encoded, and other things.

An XML document is similarly broken up into two main parts: a prolog and a document instance. The prolog provides information about the interpretation of the document instance, such as the version of XML and the document type to which it conforms. The document instance follows the prolog. It contains the actual document data organized as a hierarchy of elements.

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