DocBook provides a system for writing structured documents using SGML or XML. It is particularly well-suited to books and papers about computer hardware and software, though it is by no means limited to them. In short, DocBook is an easy-to-understand and widely used DTD. Dozens of organizations use DocBook for millions of pages of documentation, in various print and online formats, worldwide. This package contains DocBook XML versions 4.2-4.5. SGML versions are in the docbook package.