document: Quality driven web services composition The process-driven composition of Web services is emerging as a promising approach to integrate business applications within and across organizational boundaries . In this approach , individual Web services are federated into composite Web services whose business logic is expressed as a process model . The tasks of this process model are essentially invocations to functionalities offered by the underlying component services . Usually , several component services are able to execute a given task , although with different levels of pricing and quality . In this paper , we advocate that the selection of component services should be carried out during the execution of a composite service , rather than at design-time . In addition , this selection should consider multiple criteria ( e.g. , price , duration , reliability ) , and it should take into account global constraints and preferences set by the user ( e.g. , budget constraints ) . Accordingly , the paper proposes a global planning approach to optimally select component services during the execution of a composite service . Service selection is formulated as an optimization problem which can be solved using efficient linear programming methods . Experimental results show that this global planning approach outperforms approaches in which the component services are selected individually for each task in a composite service .
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