Chinese Journal of Computers   Full Text
Title	A Coordination Strategy for Reliable Service Composition and Its Analysis
Authors	FAN Gui-Sheng LIU Dong-Mei CHEN Li-Qiong YU Hui-Qun
Address	(Department of Computer Science and Engineering, East China University of Science and Technology, Shanghai 200237)
Year	2008
Issue	No.8(1445—1457)
Abstract &   Background	Abstract Service composition is an effective way to build complex Web software systems. However, the diversity of service transaction states makes it hard to guarantee reliability of the composite service. This paper presents a coordination method for constructing reliable service composition. Petri nets are used to modeling workflows, such that tasks and their relationships are articulated. Based on this, a Service Composition’s Failure Processing (SCFP) model is established according to transaction properties and service failure processing mechanisms. A coordination strategy and the corresponding enforcement method for constructing reliable service composition are proposed. Theories of Petri nets help prove soundness of the strategy. A case study of Travel Service demonstrates the usage of the coordination technique and its feasibility as well. Keywords Petri nets; Web service; service composition; transaction; reliability Background Service-Oriented Computing (SOC) is becoming the prominent paradigm for creating value-added enterprise applications by composing Web services. However, lack of reliability analysis hinders making advantage of service composition and goes against making quality software artifacts. Therefore, systematic approaches to formally analyzing and verifying service composition are very desirable. Though lots of methods have been proposed to solve the transaction properties of service composition, they mainly adopt Web services transactional protocols that are mean to develop XML-based standards for Web services. Those general protocols do not take into account the particular requirements of service consumers, thus can’t dynamically adjust according to the requirements of service consumers. Formal methods, such as process algebra and π calculus, are useful for rigorously specifying and reasoning service composition. However, due to their complex nature, they are hard for ordinary developers to use. Several researchers advocate Petri net based formalism to analyze service composition, but few of they consider the different state of transaction operation and the corresponding failure processing strategies. This paper addresses a coordination method for constructing reliable service composition. Petri nets are used to model workflows, such that tasks and their relationships are articulated. Based on this, a Service Composition’s Failure Processing (SCFP) model is established according to transaction properties and service failure processing mechanisms. A coordination strategy and the corresponding enforcement method for constructing reliable service composition are proposed, which turns to be effective. This work is partially supported by the National Natural Science Foundation of China under grants No.60473055 and No.60773094, and Shanghai Shuguang Program under grant No.07SG32.