documentation for the ports system?

[Martin Klaffenboeck]

Hello,

I know the Porter's Hanbook, but what I want to ask is:

Is there anywhere a documentation for the ports system?

How are the /var/db/pkg/* files are created.  Where comes the origin 
from and so on.  How does dynamic pkg-plist creating work?  (In ports 
which do not have a pkg-plist file)...

Is there anywhere a docu for that?

Martin