This directory contains rudimentary support for the notion of
stylesheet templates.
The idea is that if you want to change the behavior of the
stylesheets, for example, processing different bibliography
elements, you will construct a tempate document that describes
what you want and then process that template with the "template"
stylesheet.
The result of this processing will be a customization layer for
the DocBook XSL Stylesheets that does what you want. This
removes the stylesheet customizer from the burdon of figuring
out how the stylesheets work and modifying them.
In theory, anyway...