D.2 For a given system or subsystem, software is expected to be uniquely defined within a single class. If more than one software class appears to apply, then assign the higher of the classes to the system/subsystem. Any potential discrepancies in classifying software within Classes A through-- E are to be resolved using the definitions and the five underlying factors listed in the previous paragraph. Engineering and SMA provide dual TA chains for resolving classification issues. The NASA Chief Engineer is the ultimate TA for software classification disputes concerning definitions in this NPR.