VOLDEMORT (VDM)
VistA Systems are largely self describing - they know about their specific packages and configurations ("meta data"). VOLDEMORT (VDM) opens these descriptions to analysis and allows the configuration of any one VistA to be compared to any other's. VDM also contains the description of a master VistA ("GOLD") to act as the benchmark for judging any other system.
The basic flow of a VDM application is to cache a VistA's meta data, index and arrange it for ease of processing ("crunch") and produce one of more reports about the differences between that VistA and GOLD.
For more details on VDM, consult the VDM Wiki.