Service Composition for Real-Time Assurance

Service oriented architecture (SOA) has become a popular paradigm for software development in many application domains, including real-time applications. Timing analysis is a critical issue which can guide service composition to best satisfy the real time requirements of the composed system. However, existing timing analysis works do not sufficiently address some important issues. For example, admission control is an important technique for real time assurance, but most of the timing analysis techniques do not take admission control into account and, hence, may result in unrealizable decisions. Also, communication time is an important factor in real-time assurance, but most of the works do not provide clear approaches in dealing with communication time analysis. In this paper, we propose a timing specification model and analysis techniques for real-time service-oriented systems. In the specification model, a thorough consideration of all information required for timing analysis is discussed. For timing analysis, we consider the service time softly guaranteed by the admission control policy as well as estimated communication cost to reach more accurate timing estimates. Also, to avoid the analysis overhead in large-scale SOA systems, we propose a three-phase approach. In this approach, we first use a highly efficient but moderately accurate algorithm to eliminate most of the candidate compositions. More accurate timing prediction is performed on a small number of selected compositions in the second phase. In the third phase, specific concrete services are selected and admissions are performed to finalize the composition and service grounding. The approach is scalable and can effectively achieve service composition for real time requirement satisfaction.