standard XML documentation system, for software and systems DocBook is an XML document type definition (DTD). That is, it contains the "DocBook" document structure. This is used by authors or editors writing documents in the DocBook XML format. DocBook was designed for books, articles, or reference documentation about technical matters or software. It has emerged as an open, standard DTD in the software industry, and is the documentation system of choice for many free software projects. This package contains the XML DTD for DocBook, which describes the formal structure for documents following this format. If you wish to author DocBook documents using SGML rather than XML, use the 'docbook' package. You will need other packages in order to edit (psgml), validate (opensp, libxml2) or format (docbook-xsl, docbook-dsssl) DocBook documents. This package ships with the latest DocBook XML DTD, as well as a select set of legacy DTDs for use with older documents.