The Common.Change_control package contains a number of
minor problems or inconsistencies, as follows:

• the attribute 'node' in the class AUDIT_DETAILS is poorly named

• the 'description' attribute the CONTRIBUTION class should be in
  the AUDIT_DETAILS class, since any kind of audit record might
  include a description. For example, BitKeeper has description
  for both change-set and for every file changed in a change set.

• rather than inheriting from AUDIT_DETAILS, the CONTRIBUTION
  class should have an association relation with it, because
  CONTRIBUTIONS are not as such, audit objects.

• it would be simpler if the 'change_type' attribute of the class
  VERSION_AUDIT were moved to AUDIT_DETAILS, since this attribute
  could be used for audits pertaining to CONTRIBUTIONs as well.

• following the above changes, the class VERSION_AUDIT can be
  removed, and the class AUDIT_DETAILS made concrete.