DocBook is an XML vocabulary which enables you to create document content in a presentation-neutral form that captures the logical structure of the content. Using the DocBook Project XSL stylesheets, you can publish DocBook content as HTML pages and PDF files and other formats, including man pages, HTML Help, and JavaHelp.
RefDB is a reference database and bibliography tool for SGML, XML, and LaTeX documents. Command-line tools allow interactive or scriptable access to the data which are stored in a SQL database. RefDB can also be accessed through a Web interface, a SRU interface, or via editor extensions (Emacs/vim). Libraries for Perl and PHP are available for programmers. RefDB provides sophisticated character encoding handling, using Unicode by default.
oXygen is an XML editor that supports any XML document, and works with XML Schemas, DTDs, Relax NG schemas, and NRL Schemas. It has powerful transformation support that allows you to edit XSLT and XSL-FO documents and to obtain documents in the desired output format (such as HTML, PS, or PDF) with just one click. It also includes a complete Subversion client, support for flattening XML Schemata, an XML Schema instance generator, integration with the X-Hive/DB, MarkLogic and TigerLogic XML databases, editing actions on the diagram, and a rename refactoring action.