odel, design, and deploy the dynamic composi- tion of services, that we present in this chapter, was first introduced in Rossebo and Brak [3]. For modeling the choreography of service collaborations, the approach uses the concept of a policy enforcement state machine (PESM) and composition policies, which we elaborated on in Rossebo and Runde [4], and in Rossebo [5]. Essentially, the global PESM is similar to a UML 2.x activity diagram with collabo- ration uses as nodes. The approach is presented in this chapter along with a methodology explaining how to use UML 2.x, PESMs, and composition policies to model, design, and deploy the dynamic composition of services. We exemplify the approach and meth- odology using a tele-consultation service. The rest of the chapter is organized as follows: In Section 5.2, we provide an overview of the policy-based approach to dynamic composition, and in Section 5.3, we introduce the tele-consultation service used in the remainder of this chapter. In Sections 5.4 and 5.5, we explain how we model service composition, introducing some basic terminology and presenting first the global PESM diagrams at the ser- vice model layer, and then their transformation into local PESM diagrams, one for each composite role, at the design model layer. The methodology is presented in Section 5.6 and is explained in Section 5.7 as to how to use the methodology to change and adapt existing services. Related work is presented in Section 5.8, before concluding in Section 5.9. 5.2 Overview of the Policy-Based Approach A graphical overview of the model-driven, policy-based approach to dynamic ser- vice composition is provided in Figure 5.1. At the service model layer, services are Service Delivery Platforms Service models Policy rules UML collaborations Policy Rule ID Condition Trigger Action PDP1_rul P1, A.x, B.y Do CU1 A.gl, B.g1 PDP2_rul P2, A.t, C.r Do CU2 A.g2, C.g2 PDP2_ru2 P3,B.f,C.g Do CU3 B.g3, C.g3 Model transformation Design models Local PESMs Local policy Systems Components Policy rule ID Cond