request message to the remote agent that manages actor 12. This message is defined in the association protocol part of the agent layer protocol. The remote agent looks up (in its T-AL table) which AAI connects the element 12 (if any) and offers this actor, in an agentAssociationOffer(1 As, 1 ASi) primi- tive (agAssOff(...) for short), the association to actor 11. If actor 12 accepts the offer it answers with an agAssAcc(1 ASi) primitive. The establishment phase then ends with an acAssCnf(1 ASi) primitive to actor 11. 2.3 Agents and Actors From here on, actors 11 and 12 invoke each other by r-invokeOrd(1 ASi,...) and I-invokeRep(1 ASi,...) which are mapped on messages of the remote operation protocol, which is the other part of the agent layer protocol. Before the actors end the dialogue voluntarily, an agent may detect problems that forces it to release the association. These problems could be related to the connectivity layer it uses, local processing problems, actors creating invalid invokes, or a remote agent sending invalid messages. In any case, the agent informs its own actor by an agentReleaseReport(1 ASi) primitive (agRelRep(...) for short) and sends a corresponding message to the remote agent that does the same to its actor. Normally (hopefully) the actors release their association voluntarily. The initiat- ing actor does that by an actorReleaseOrder(1 ASi,...) primitive (acRelOrd(...) for short). Its agent sends a message to the remote agent, that informs its actor by an agRelRepReport(1 ASi,...) primitive that the other actor has released the association. By this scenario we have identified a minimum set of four operations that are needed in a SAG to support associations: acAss (operation class is REQUEST), agAss (operation class is OFFER), agRel (operation class is REPORT), acRel (operation class is ORDER)¹7. The parameters of these operations consists of actor suffixes and association identifiers, as indicated in the scenario. In addition, the acAssReq and agAssOff primitives may include other parame