Time and Cost Aware Instantiation of Composed Services

Service level agreements frequently specify which durations of a service a client may choose when invoking the service and their respective price. Information about the relationship or trade-off between price and duration is relevant for selecting a service. It is the basis for various optimizations, e.g., minimizing or maximizing the duration of a service within a given budget or minimizing cost for admissible durations. Service providers, therefore, have to express the relations between time and cost. Service clients may choose a specific duration of a service invocation for the respective price. The service provider then has to instantiate the composed service and invoke component services by selecting parameters in such a way that the temporal service guarantees are fulfilled. We present a technique for computing the duration parameters for invoking component services in a way that the overall cost is minimal for the provider of the composed service. We formally define this technique and demonstrate its feasibility and scalability with a proof-of-concept implementation.