A real-time perspective of service composition: Key concepts and some contributions

Timing predictability of service oriented architectures is challenged by their dynamic nature. Systems have to reconfigure their service-based structure to adapt to the changing environmental requirements. The development of dynamic systems that have timing constraints is currently not possible without imposing some bounds and limitations to the structure and operation of the system. This paper identifies the key factors for achieving time-bounded service-based reconfiguration from a system perspective. The key contribution to bypass the possible complexity of the used task model and associated schedulability analysis algorithm is the provided architectural design that separates the composition from the schedulability. The paper also extends a previous service composition algorithm that provided a feasible solution compliant with the application quality of service criteria (QoS). Due to the design based on the separation of concerns, the algorithm is a simple straight forward graph search guided by values related to the application QoS. The generalized algorithm offers a search mechanism guided through n regions going beyond the four regions model of the previous contribution. Results from the previous algorithm and the n regions version are shown to illustrate the advantages and finer grain results of the latter.