DocBook

DocBook is a semantic markup language for producing technical documentation. It defines a vocabulary and a set of structures for describing the logical content of a document—such as books, articles, chapters, sections, figures, and tables—without prescribing presentation. Documents written in DocBook can be transformed into multiple output formats, including HTML, PDF, man pages, and ePub, using stylesheet pipelines.

DocBook originated as an SGML DTD designed to standardize technical documentation for UNIX and open-source projects. With the rise of XML, the DocBook community published the XML-based DocBook 5 specification, maintained by OASIS. The DocBook family is modular, with defined top-level elements like book, article, and chapter, and a rich set of content elements for program listings, code, equations, graphics, and cross-references. Authors typically store content in XML or SGML and validate against a DTD or schema.

Processing toolchains commonly rely on the DocBook XSL Stylesheets (docbook-xsl) to transform content into HTML or XSL-FO; the latter can be rendered to PDF with engines such as Apache FOP or other XSL-FO processors. The ecosystem includes editors, validators, and repository tooling; many open-source projects and Linux distributions use DocBook for manuals, man pages, and technical references.

DocBook is favored for documentation that needs clear structure, reliable cross-referencing, and multiple output formats, rather than tight layout control. Overall, DocBook remains a widely supported standard for technical documentation in both SGML and XML forms.