The element <groupNumber> contains a number or other identifier associated with major components, assemblies, and subassemblies that form functional groups. Subordinate, sub-functional groups or sub-subassemblies relate to the base group number (top position) in a sequential, next higher assembly (NHA) relationship (ie, top-down breakdown structure). The functional group applies to repairable assemblies and subassemblies, for example, spares (any repairable component required for the maintenance or repair of an end item), but not to repair parts (any consumable, non-repairable component required for the maintenance or repair of an end item).