XML Companion, The, Third Edition

Introduction

It is possible to create valid and useful XML documents using nothing but the markup already introduced. The markup described in the previous chapter performs the important task of creating a self-describing document, including useful meta-data. However, elements and attributes are essentially passive explanations of the document contents. Software can choose to ignore some or all of this markup. Almost all of the remaining XML features are much more active, and are mainly instructions to software to perform certain operations.

This includes comments to the document author, links to a DTD or stylesheet, clarifications on the character set and version of XML the document conforms to, and identification of sections of the document ...