iagram for the tele-consultation case with authentication added. Service Delivery Platforms sd UniTwoPassAuthenticate authenticatee : authenticator : Challenge responder challenger authenticatee: authenticator : responder challenger Generate challenge Challenge_signal Challenge Generate response Response Response authenticatee : authenticator : responder challenger Validate response Response_signal [Response Valid] Ok_signal Unilaterally_Authenticated [Response NOTValid] NOk_signal NotAuthenticated Figure 5.25 UML 2.x sequence diagram for the UTPA collaboration. The global PESM diagram is modified during the reiteration of Step 3 by adding the pas collaboration use of UTPA as a node prior to the collaboration use prs of registration in the teleconsultation PESM with PDP inserted following the node, as shown in Figure 5.26. Additional policy rules are specified for PDP1, and policy rules are identified by the newly inserted PDP4. Existing policy rules may be changed, as exemplified by the changes to the condition part of PDP5 Rule1. While we have chosen to exemplify the addition of authentication to the service using the UTPA collaboration, the approach and methodology allow for a choice of different authentication collaborations to be specified as described in Rossebo [5]. The UTPA collaboration may also be further specialized depending on protocol and algorithm to be used [5]. How to Model Dynamic Service Composition Using UML 2.x PESM Teleconsultation with authentication PDP1_Rule3: T: ? (Request registration, External, PatientT) C: Rel(PatientT.secret, TeleSvcDsK.knowledge), Patient T.True, TeleSvcDsk.(Unilateral required and Challenge required) G: PatientT.unilaterally_authenticated TeleSvcDsk.authentication_successfu PDP1_Rulel: PDP1_Rule2: T: ? (Request authentication, External, PatientT) T: ? (Request registration, External, Patient T) C: Rel(PatientT.secret, TeleSvcDsK.knowledge), C: Patient T is a Patient of Doctor, PatientT.True, TeleSvcDsk.(Unilateral PatientT.NeedsAssistance, required and Challenge re