on (err) SW model internal resource relation (irr) Instances: SW1,SW2 con To connects To Fig. 6.19 External resource relations in CNPC The external resource relations in Fig. 6.19 are set by relating identifiers for channels (chld) to identifiers of positions in switches (posId). CNPC now has a model that gives the complete picture of the resource system for creating connec- tions. However, when CNPC communicates with TEPC, the model CNW simpli- fies this picture SO that TEPC and CNPC can talk about network-wide connections only. This requires that CNPC can map a connection over the routes and switches that are used for that connection. This mapping is defined by abstrac- tion relations between the CNW model and the models of inter-service related resources, according to Fig. 6.20. If we add all the properties that were defined pre- viously for the service resource models to the object resource model of Fig. 6.20, we have the complete object resource model for the agent CNPC. 6 Process Control System Modelling CNW model Connection Connection Connection endpoint Network 1,2,30 requires conTo conTo *) The two endpoints must not belong to the AccessRoute Switch SwitchRoute same route or InternalRoute*) con To conTo 1,2,30 conTo conTo Channel Position Channel external resource relation abstraction relation Fig. 6.20 The object resource model for CNPC The object resource model for TEPC is created by defining abstraction relations between the TNW and CNW models, and external resource relations between the CNW model and teleservice resource models (TR), see Fig. 6.21. The CNW model in TEPC is an abstraction of the model in Fig. 6.20, and considers only such entities and properties that TEPC needs for communication with CNPC. It assumes that each terminal system has only one CNU. A CNU can therefore be identified by a TR-SAPIs. It is also assumed that the CNPC informs the TEPC when access and internal routes become blocked and deblocked. TNW model in TEPC Terminal #*TE-SAPI System dependsOn Simplified CNW model in TEPC C