1. The "metadata" database is pretty cheesy. It only supports URNs and
   directions. The whole metadata concept needs some thinking.
2. The tying of DCN information to the measurable elements is pretty cheesy. We
   use URNs for the most part. For static stuff, this is straight-forward. For
   the dynamic stuff, this gets awkward since there's no good way to convert
   eth port + sonet port + vlan into the two measureable entities. The
   workaround is to have the collector convert a "vlan" element into a port
   with identifier [eth_port]_[vlan], and it has the complete data, i.e. the
   sonet port is completely hidden.
3.
