Automatic discovery and composition of Web services is an important research area in Web service technology, in which the specification of Web services is a key issue. This paper presents a Web service capability description framework based on the environment ontology. This framework depicts Web services capability in two aspects： the operable environment and the environment changes resulting from behaviors of the Web service. On the basis of the framework, a requirement-driven Web service composition model has been constructed. This paper brings forward the formalization of Web service interactions with π calculus. And an automatic mechanism converting conceptual capability description to the formal process expression has been built. This kind of formal specification assists in verifying whether the composite Web service model matches the requirement.
HOU Lishan1,3,JIN ZHi1,2 & WU Budan1,4 1. Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100080, China
Understanding the meaning of requirements can help elicit the real world requirements and refine their specifications. But what do the requirements of a desired software mean is not a well-explained question yet though there are many software development methods available. This paper suggests that the meaning of requirements could be depicted by the will-to-be environments of the desired software, and the optative interactions of the software with its environments as well as the causal relationships among these interactions. This paper also emphasizes the necessity of distinguishing the external manifestation from the internal structure of each system component during the process of requirements decomposition and refinement. Several decomposition strategies have been given to support the continuous decomposition. The external manifestation and the internal structure of the system component have been defined. The roles of the knowledge about the environments have been explicitly described. A simple but meaningful example embedded in the paper illustrates the main ideas as well as how to conduct the requirements decomposition and refinement by using these proposed strategies.
