rks in protocol networks (integration step 2) 7.7.2 Integration Mechanisms The operation handler (OPH) and the object handler (OBH) represent the integra- tion mechanisms in abstract networks. Creating the OPH is basically a matter of collecting all operation specifications that concern a particular abstract protocol in a common port object, and interfacing that object to a message-handling function (MEH). The OPH is also assumed to know the primitive service identifier (PSid) of all service ports in its own abstract machine. The OBH is an extra service object that is added to an abstract machine when there is a need for it. An OBH provides a service relation handling function. This is a function that establishes and releases service relations, identified by service rela- tion identifiers (SRid), between objects of the same abstract protocol. The function is needed when object access must be dynamic, when there can be more than one service relation active simultaneously and when there are several alternative detec- tors for provider initiated events. Sometimes service relations are implicitly identi- fied by using primitive service identifiers as part of events. Mostly, however, an explicit access procedure, handled by the OBH, is required. Figure 7.64 (based on Fig. 7.62) is used to discuss different access problems, to be solved in abstract pro- tocols. 7.7 Concepts and Notations in Abstract Networks S4 AG4 Fig. 7.64 Access problems in abstract networks 1. The relation between VO1 and AG4 could have been used by simply including the primitive service identifier S6 in communication events. This would not require an OBH in AM1. The OPH (not shown) would know which object to address, since there is only one object that handles S6 in each of AM1 and AM3. However, the object VO1 is defined as non-persistent in this service network, maybe because it may not be used concurrently by several users. This implies that the service relation will be a temporary relation (an SRid) that must be set up before it can be used, an