view diagram from Step 1 using 1. A global PESM diagram for describing the ordering of the collaboration uses. 2. A set of global policy rules for each PDP in the global PESM diagram, using the precise syntax given in Rossebo and Runde [4]. Together, these policy rules constitute the composition policy for the composed service. sd call caller : Caller callee : Callee CallRequest(caller, callee) Busy(callee) Ringing(callee) Answer {Caller.calling} {Callee.called} Connected Hangup {Caller. :TalkedTo(Callee)} {Callee.TalkedTo(Caller)} Disconnected NoAnswer [time out] Figure 5.18 UML 2.x sequence diagram for the call collaboration. Service Delivery Platforms Step 3 applied to the tele-consultation service: The global PESM diagram for the tele-consultation service is described in this step along with the global PESM dia- grams for each of the composed subservices, aided Registration and con- sultation, used in the tele-consultation service. The PESM diagrams and policy rules have been explained in Figures 5.7 through 5.9 of Section 5.4. 5.6.2 Methodology: The Design Model Layer At the design model layer, the overall service behavior described at the service model layer is broken down for each composite role separately. In this section, we address the methodological steps performed in order to achieve this. Step 4: Create elementary role state machines For each elementary collaboration not taken from the repository but specified in Step 2, create one elementary role state machine for each of the two roles involved in the collaboration. The transformation from sequence diagrams to elementary role state machines may be performed manually or automatically as described in Whittle and Schumann [17] and Seehusen and Stolen [18]. Step 4 applied to the tele-consultation service: As examples, Figure 5.19 shows the elementary role state machines for the caller and callee roles involved in the call collaboration. The elementary role state machine for caller is generated from the caller lifeline of the call sequence diagram in Fig