DocBook is not really a TeX alternative, since it is merely a markup language and does no typesetting of its own. There are actually many DocBook workflows that do the final typesetting in TeX.
Actually, I think this is an asset. DocBook is modular, and consists of DTDs/schemas and stylesheets to translate DocBook content to other XML documents (or plain text). Since TeX is so tightly-coupled to typesetting, it kinda sucks for producing non-typesetted formats.
Using TeX to do the final typesetting in a DocBook workflow is quite old-fashioned. For years, I have used the XSL-FO stylesheet to create XSL-FO output. You can pass this to an XSL-FO typesetter, such as Apache FOP or RenderX.
This workflow has several advantages:
* You can easily tweak output by overriding templates.
* Commonly-used FO renderers render SVG and MathML. You can use one vector graphics format to create XHTML, ePub, and PDF/print output.
* Each step and output, except for the rendering step is XML and can be validated and transformed easily.
Yup, except that XSL-FO output is of shitty quality, especially if you are doing heavy math typesetting, and I know at least one pretty successful open access publisher doing this DocBook->TeX workflow for all their puplications.
