Research On Compatibility And Mediation Of Web Service Interfaces

Web services have provided syntactic interoperability for disparate applications on the Internet by using a series of standard specifications.Siuce interacting applications based on Web services only need to obey their respective interfaces,their coupling degree can be reduced and the flexibility of them can be increased a lot. Therefore,the Web services technology is becoming a major approach to enterprise application integration and business to business interactions.Since Web services based systems are loosely coupled,a new issue occurs:how to ensure that two Web service interfaces can interoperate when they are developed independently? Current Web services technology just offers syntactic interoperability for autonomous Web service interfaces while the semantic interoperability of them is still an open problem.This dissertation uses a formal approach to address the compatibility and mediation issues of Web service interfaces.The main contents of the dissertation are as follows:1) How to determine the information a Web service interface needs to include is studied.Based on an analysis of the interaction behaviors of Web services,we point out that a Web service interface should contain two parts:messages and a process. While the messages part defines the schemas and directions of messages the interface supported,the process part defines a process that puts ordering constraints on the message exchanges.2) The message compatibility between Web service interfaces is studied.First, we present an ontology based approach to semantically annotate message schemas, and propose a formal model for the annotated messages.Then,we define the message compatibility based on the formal message model and devise a message compatibility check algorithm.In order to dealing with incompatible messages,we also propose a quantitative approach to measure the compatibility degree of messages and devise an algorithm to compute the message compatibility degree.3) The process compatibility between Web service interfaces is studied.We first propose a formal model for Web service processes and provide rules to transform process descriptions to corresponding models.Based on the formal process model,we define three exception properties of Web service interactions:unspecified reception, deadlock and livelock.Then,we define the process compatibility based on the three exception properties and devise a process compatibility check algorithm.In order to dealing with incompatible processes,we also propose a quantitative approach to measure the compatibility degree of processes based on the three exception properties and devise an algorithm to compute the process compatibility degree.4) The mediation methods for incompatible Web service interfaces are studied. For incompatible messages,we first define two kinds of mediation rules:attribute mediation rule and element mediation rule,which are used to convert messages,and then devise the algorithms for generating the attribute mediation rules and element mediation rules.For incompatible processes,we first extend the Web service process model to cater for mediation processes,and then devise an algorithm to synthesize the mediation process from incompatible processes.Based on the presented definitions of the compatibility and reliability of mediation processes,we also prove that a mediation process synthesized by the algorithm is compatible and reliable with the mediated processes.