Metadata - can it query database/xml file?

System

pretty much instead of using a static list setup in the web client, we would like a few of our MediaBin metadata items thats are very long and updated frequently to be called from a database or from an xml file. i know when u export a metadata item its xml, but i couldnt find where they are being referenced in the MB folder structure. are they stored natively as xml or soemthing else?