Editing DocBook (section)

== History ==

DocBook began in 1991 in discussion groups on [[Usenet]] and eventually became a joint project of [[HAL Computer Systems]] and [[O'Reilly Media|O'Reilly & Associates]] and eventually spawned its own maintenance organization (the Davenport Group) before moving in 1998 to the ''SGML Open'' consortium, which subsequently became [[OASIS (organization)|OASIS]]. DocBook is currently maintained by the ''DocBook Technical Committee'' at OASIS.<ref>[http://www.docbook.org/tdg5/en/html/ch01.html Getting Started with DocBook]</ref>

DocBook is available in both [[SGML]] and [[XML]] forms, as a [[Document Type Definition|DTD]]. [[RELAX NG]] and [[W3C XML Schema]] forms of the XML version are available. Starting with DocBook 5, the RELAX NG version is the "normative" form from which the other formats are generated.

DocBook originally started out as an SGML application, but an equivalent XML application was developed and has now replaced the [[SGML]] one for most uses. (Starting with version 4 of the SGML DTD, the XML DTD continued with this version numbering scheme.) Initially, a key group of software companies used DocBook since their representatives were involved in its initial design. Eventually, however, DocBook was adopted by the open source community where it has become a standard for creating documentation for many projects, including [[FreeBSD]], [[KDE]], [[GNOME]] desktop documentation, the [[GTK+]] [[Application programming interface|API]] references, the [[Linux kernel]] documentation (which, as of July 2016, is transitioning to [[Sphinx (documentation generator)|Sphinx]]/[[reStructuredText]]<ref>{{Cite web|url=https://www.kernel.org/doc/html/v4.8/kernel-documentation.html|title = Linux Kernel Documentation — the Linux Kernel documentation}}</ref><ref>{{Cite web|url=https://lwn.net/Articles/692704/|title = Kernel documentation with Sphinx, part 1: How we got here &#91;LWN.net&#93;}}</ref>), and the work of the [[Linux Documentation Project]].

=== Pre DocBook v5.0 ===

Until DocBook 5, DocBook was defined normatively by a Document Type Definition (DTD). Because DocBook was built originally as an application of [[SGML]], the DTD was the only available schema language. DocBook 4.x formats can be SGML or XML, but the XML version does not have its own namespace.

DocBook 4.x formats had to live within the restrictions of being defined by a DTD. The most significant restriction was that an element name uniquely defines its possible contents. That is, an element named <code>info</code> must contain the same information no matter where it is in the DocBook file. As such, there are many kinds of info elements in DocBook 4.x: <code>bookinfo</code>, <code>chapterinfo</code>, etc. Each has a slightly different content model, but they do share some of their content model. Additionally, they repeat context information. The book's <code>info</code> element is that, because it is a direct child of the book; it does not need to be named specially for a human reader. However, because the format was defined by a DTD, it did have to be named as such. The root element does not have or need a ''version'', as the version is built into the DTD declaration at the top of a pre-DocBook 5 document.

DocBook 4.x documents are not compatible with DocBook 5, but can be converted into DocBook 5 documents via an XSLT stylesheet. One (<code>db4-upgrade.xsl</code>) is provided as part of the distribution of the DocBook 5 schema and specification package.<ref>Jirka Kosek, Norman Walsh, Dick Hamilton, and Michael Smith, ''DocBook V5.0: The Transition Guide'', 16 June 2009, [http://docbook.org/docs/howto/#convert4to5 Converting DocBook V4.x documents to DocBook V5.0]</ref>