where does macports store it's installed application database?

[Panayotis Katsaloulis]

I am in the process of creating a front-end for macports, and I wanted to know where does it store the list of installed applications.
I've found, for example in the default installation, that the list of available ports is found under 
/opt/local/var/macports/sources/rsync.macports.org/release/ports/PortIndex

which is convenient and easily parsable.

What about the applications that are installed or need to be upgraded, or are obsolete?

 P.S. is someone wants to beta test my application (which is open source of course), I'd be glad to collaborate and listen to a second opinion.
I've just uploaded it to google code here:
https://code.google.com/p/cafeports/