# J.1. DocBook

The documentation sources are written in *DocBook*, which is a markup language defined in XML. In what follows, the terms DocBook and XML are both used, but technically they are not interchangeable.

DocBook allows an author to specify the structure and content of a technical document without worrying about presentation details. A document style defines how that content is rendered into one of several final forms. DocBook is maintained by the [OASIS group](https://www.oasis-open.org/). The [official DocBook site](https://www.oasis-open.org/docbook/) has good introductory and reference documentation and a complete O'Reilly book for your online reading pleasure. The [NewbieDoc Docbook Guide](http://newbiedoc.sourceforge.net/metadoc/docbook-guide.html) is very helpful for beginners. The [FreeBSD Documentation Project](https://www.freebsd.org/docproj/) also uses DocBook and has some good information, including a number of style guidelines that might be worth considering.


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