[optimization] traced_selection is used very intensively in debug mode
optimizing it is worth the pain. Basically : don't do stuff unnecessary
when we don't trace anything.
Schema of the data
------------------
First take a look at the data schema_ then try to remember that you are browsing
through a heap of data by applying stylesheets to the results of queries. This
site is not a content management system with items placed in folders. It is an
interface to a database which applies a view to retreived data.
.. _schema: schema