The MODULE-IDENTITY macro is used to provide contact and revision history for each information module. It must appear exactly once in every information module. It should be noted that the expansion of the MODULE-IDENTITY macro is something which conceptually happens during implementation and not during run-time. Note that reference in an IMPORTS clause or in clauses of SNMPv2 macros to an information module is NOT through the use of the 'descriptor' of a MODULE-IDENTITY macro; rather, an information module is referenced through specifying its module name.