SGML is the Standard Generalized Markup Language. It's a meta-language that is used to describe text markup languages, such as HTML. It's a very flexible system that allows a very broad range of possibilities.
The main power that you gain is the ability to write your own markup language for specific purposes. HTML was one of them. There are other common SGML applications (called 'DTD's) such as DocBook that are used for specific purposes.
Where I Come In
But, true to form, I wasn't happy with any of 'em. Sure, HTML is great for pure hypertext markup. Sure, DocBook is great for generalized documentation. But I had more specific needs.
So, this is my collection of SGML applications that I've written. They also include transformation stylesheets in DSSSL, which is a language intended to allow transformation and styling of SGML applications. I use it to generate formatted versions of the input documents, in formats like HTML, PostScript, PDF, etc.
What They Are
These pages include information on the following DTD's I've written.
A DTD and stylesheet set designed for marking up documentation of a code library. This was designed and developed specifically for the libpostal project, and remains developed as a part of it.
A DTD and stylesheet set for marking up a resume. I use this for my resume, and it should be sufficiently generalized to work for a large number of cases.