Everything I write in this category is XML markup that validates to a semantic language known as DocBook 5.0. Some of the content is reverse-engineered from old original documents and websites. The rest is being re-written to validate to a RELAX NG schema and integrated with Schematron rules.
My aspiration is to create a valid DocBook plugin for WordPress. I think WordPress is an outstanding content management system and I wish I had started using it years ago.
In the meantime, take a look at the links below. They prove the concept of single source publishing by showing examples of XML code processed into other web formats like: XHTML, Web Help (including DITA) and, of course, PDF. The original site is a highly styled XHTL site and written before I discovered WordPress.
XML Design Concepts | Well Formed XML | XML Validation | XML Deployment