m, which automatically determines the need to change or upgrade the service. As can be seen by this example, it is not enough to deploy services rapidly, as the dynamic service environment is changing continually, requiring services to be adaptable at runtime also. By this we mean, that in addition to being able to rapidly deploy new services, it must be possible to dynamically change existing services at runtime to adapt to conditions in the service environment that were not foreseen when the service was originally deployed. This chapter addresses the problem of rapid development and dynamic deploy- ment of services in the converged service environment. We present a policy-driven How to Model Dynamic Service Composition Using UML 2.x approach to service modeling, design, deployment, and implementation. In the approach, policies are used both for monitoring, and for describing the composition of services, where a policy is a set of rules defining choices in the course of the behavior of a system. A service is an identified functionality (i.e., behavior) involving a collaboration among entities in order to achieve some desired goals/effects for end users or other entities. One important aspect of services is that they normally are partial function- alities that cross-cut the component structure SO that a service may involve several collaborating components while each component may participate in several services. Service composition addresses the means of composing the partial behaviors of col- laborating components in order to achieve the overall service. We model a service as collaboration among roles with associated behavior, using the Unified Modeling Language (UML) version 2.x [1]. The basic building blocks for composed services are elementary service collaborations between two entities collaborating on an inter- face to provide a service or a service feature [2]. The visible interface behavior asso- ciated with an elementary collaboration is modeled using UML 2.x interactions. The policy-driven approach to m