Formal Approaches to Service-oriented Design : From Behavioral Modeling to Service Analysis

Abstract: Service-oriented systems (SOS) have recently emerged as context-independentcomponent-based systems. In contrast to components, services can be created,invoked, composed and destroyed at run-time. Services are assumed to be plat-formindependent and available for use within heterogeneous applications. Oneof the main assets in SOS is service composability. It allows the developmentof composite services with the main goal of reusable functionality providedby existing services in a low cost and rapid development process at run-time.However, in such distributed systems it becomes difficult to guarantee the qual-ity of services (QoS), both in isolation, as well as of the newly created servicecompositions. Means of checking correctness of service composition can en-able optimization w.r.t. the function and resource-usage of composed services,as well as provide a higher degree of QoS assurance of a service composi-tion. To accomplish such goals, we employ model-checking technique for bothsingle and composed services. The verification eventually provides necessaryinformation about QoS, already at early development stage.This thesis presents the research that we have been carrying out, on devel-oping of methods and tools for specification, modeling, and formal analysisof services and service compositions in SOS. In this work, we first show howto formally check QoS in terms of performance and reliability for formallyspecified component-based systems (CBS). Next, we outline the commonali-ties and differences between SOS and CBS. Third, we develop constructs forthe formal description of services using the resource-aware timed behaviorallanguage called REMES, including development of language to support servicecompositions. At last, we show how to check service and service composition(functional, timing and resource-wise) correctness by employing the strongestpostcondition semantics. For less complex services and service compositionswe choose to prove correctness using Hoare triples and the guarded commandlanguage. In case of complex services described as priced timed automata(PTA), we prove correctness via algorithmic computation of strongest post-condition of PTA.