A maintenance system can be assessed by looking at the output - at the end results it achieves, or by assessing it as a process whose elements are defined and managed in accordance with some standard or some established procedures. Whilst the end result cannot be ignored as a measure of the effectiveness of a Maintenance System this handbook concentrates on the assessment of the process itself.

It is the KOM Maintenance System that forms the primary focus of concern and other issues are regarded as inputs, outputs or sub-routines operating on that central process. KOM Maintenance System gives advice and guidance on fundamental structural and organizational elements involved in a Maintenance System and on methods to establish their existence, their degree of sophistication and their effectiveness.

At the practical level of maintenance tasking, Maintenance System concerns itself with machinery systems and related services, such as instrumentation, rather than with structural, process or electrical system maintenance, but the general principles concerning Maintenance Systems are relevant to all.