pkg
CLIENT DEDUCTION AND SELF-REPAIR

  In the case of a partially installed system, a system installed by a
  previous packaging regime, or a system that has been somehow damaged,
  it is possible for the pkg system to identify the current system's
  state via a deductive process.

  That is, the client can examine an image's contents and determine, by
  interrogation, the precise version of each package installed in the
  image.  If a specific file is missing, then the client can move the
  package from (INSTALLED, .) to (INSTALLED, damaged) and record the
  operation it would take to restore the package's state (via restoring
  the contents).

  XXX Most efficient algorithm for the minimum set of queries to
  identify the specific version of a package an image contains?