/var/lib/rpm/status -
          it's timestamp/counter determines if the rpmdb has been modified. Along with other immediate and useful information - maybe even write it out as an index

/var/lib/rpm/packages
        name[0]/name[1]/name/arch/epoch-ver-rel/
                        filelists - with md5sums? properties/owner/mode?
                        conffiles - include in above?
                        requires
                        provides
                        obsoletes
                        conflicts
			scripts
                        signatures
                        changelog
           questions:
                  - should it be one file per tag for some of the data?
                       - description, summary, sourcerpm, license, 
                          buildhost, etc?
                  - what format should the formatted data be
                             - xml?
                  - locking semantics
                  - searching rapidly
                  - indexes?