Communications network having management system architecture supporting reuse

A communications network, eg a distributed network, comprises a plurality of distributed physical resources in the form of components, assemblies of components (604), and systems based on components and composites. A network management system of such a network comprises an application level (600) which represents the functionality of a plurality of different composites being hardware and/or software components of different proprietary manufacture and different function capability, and an implementation level (601) which implements control of the composites. The application level is sub-divided into a plurality of application level elements each of which correspond to a function capability of a composite or system, a system being a highest level of composite. The implementation level is sub-divided into a plurality of implementation level elements each of which represents a system, a composite or a component. The internal structure of the elements within the application controller and implementation level corresponds to internal architectures of the systems and composites.