horeography is hardcoded. With our approach, dynamic coordination of the elementary collaborations and the conditions for choosing between alternative collaborations are governed by com- position policies. Using policies for this purpose provides flexibility, in that the exact set of elementary collaborations involved in the composed service, and the ordering of these is determined first when the service is actually executed in the runtime sys- tem. Separating the specification of the policy rules from the collaborations, also allows for changes to be made at runtime by changing the policy rules without changing the service parts themselves. Our approach allows for dynamic adaptation by using policies to link together the separately specified collaborations. Adaptation is possible when triggered by an event or when policy rules are changed to allow for insertion of new behaviors. In Castejón et al. [23] and von Bochmann [24], the authors focus on describing how UML collaborations can provide a framework for service modeling that enables service behaviors to be completely defined, and analyzed for problems. This pro- vides a strong basis for analyzing problems that can arise in service composition that may lead to realizability problems such as race conditions. We have not focused on addressing such realizability problems, but rather have focused on the problem of enabling dynamic service composition. In Castejón et al. [23] and von Bochmann [24], the authors have integrated the specification of which role plays the initiating role and which role plays the partici- pating role in the specification of the subordinate collaborations in order to analyze behavior with respect to realizability, and to synthesize role behaviors. In Castejón et al. [23] and von Bochmann [24], there is no management layer present in the approach, and therefore the authors must make demands on the ordering of initiat- ing and terminating roles in order to avoid realizability problems. Alternatively, the authors could have used synchronizat