QoS-aware automatic syntactic service composition problem: Complexity and resolution

Automatic syntactic service composition problem consists in automatically selecting services, from a registry, by matching their input and output data. The composite service, resulting from this selection, allows producing a set of output data, needed by a user, from a set of input data, given by the user. Many approaches resolving the aforementioned problem do experimentations on the well-known Web Service Challenge (WSC) standard benchmark, which provides synthetic services. Since 2009, this challenge has extended the syntactic service composite problem to a Quality-Of-Service (QoS) based one, by describing the synthetic services with execution time and throughput values. In this article, we propose an original formulation of the QoS-aware automatic syntactic service composition problem in terms of scheduling problem with AND/OR constraints, using a directed graph structure. For the WSC-09 benchmark (considering execution time and throughput QoS criteria), our exact algorithm outperforms the related work. We also analyse the complexity of optimizing other QoS criteria (cost and reliability) and exhibit polynomial cases.