Apache modules for serving DocBook

I have a series of chapters (marked up with DocBook XML) stored in a 
mysql database.  I would like them to be rendered as both HTML and pdf 
through a webpage. This is creating an online book.

What is the preferred / efficient method to automate this using apache 
?  Do I need to run an XSLT and XSLFO each time?  I would prefer not to 
store the HTML and pdf, but create them on the fly if that is not to 
time consuming.  Most chapters are about 2500 words of text, plus 
markup, which can be up to 50% more.  Images are also present.

Cheers,

Tristan
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Tristan J. Fiedler
Postdoctoral Fellow - Stein Lab
Cold Spring Harbor Laboratory