ebuild db

[doug-x07]

I was just playing around trying to hack some tools for managing packages whilst looking through the /usr/bin/qpkg source. My question is where can I find out a bit more about how the /var/db/pkg files are structured? I kind of gathered that the COUNTER file holds the installation order count of an ebuild and that /var/cache/edb/counter contains the current ebuild counter token. Is this right? What are the PROVIDE and PF files used for? The structure seems to always be in the group/ebuild name/values format. Is that systematically the case or are there any exceptions to the rule?

If anyone has been doing similar stuff, can give me some information or point me to any resources it would be greatly appreciated.
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#! /usr/bin/perl
if( @first != $succeed ) {
post { $question->forum && eval '$answers' };
try { $again } catch { $problem && $resolve };
bless $posters; }