ing, the consumer must actively ask the event channel object if any event of interest has happened, and a supplier object must announce its presence, as well as the events it can report, to the event channel object. The picture we have given on how spontaneous events are handled in different management concepts is scattered, and (as can be expected) comprises different solutions, concepts, and terms. To use the AMLn actor-agent separation and AMLs operation classes (in particular such classes where the "event supplier" initiates operations, i.e., REPORT, OFFER and INVITE), could improve this situation con- siderably. The Management System 5.4.1 Introduction Since a management system (normally) has to manage a large set of distributed net- work elements, it is a network system in itself. It can therefore be modeled as any other network system, i.e., by a layer structure and a logical network structure. From a functional point of view, it has a simpler structure than traffic systems because all management functions (AFs, OSFs and the agent layers on which they rely) belong to a single management layer in the management plane. This layer extends into the network elements that are managed. Since the whole layer is a con- trol layer, we can simplify its model by showing its layer state machine (LSM) rep- resentation, thereby eliminating agent layers and layer protocol machines (LPM). The LSM structure, in its simplest form, would then look like Fig. 5.10, consisting of a single OSF and a strictly hierarchical structure of element state machines (ESM). The ESMs that concern the management system are the AFs, the OSF, and the WSF (which are ESMs that are also defined in TMN). We added the operator function (OPF) and therefore also the work station function (WSF) to avoid forget- ting that there are users of the layer who have the overall control of everything that happens (or shall happen) in, or related to, the traffic system. 5.4 The Management System Fig. 5.10 A single OSF managing all traffic system nodes. Shaded ES