A Research On Web Services Discovery And Composition Based On Semantic Web Technology

With the advent and popularization of e-commerce and e-government, it is requisite that the distributed and heterogeneous business applications can be integrated and interoperate with each other in the environment of Internet. And it is also requisite that the appropriate business applications over the Internet can be rapidly and automatically found according to the demand and that they can be composed to meet the demand if there exists no individual business application to meet the demand. Web services technology is quite promising for the integration of business applications and service composition. Web services are more coarse-grained and operate at a higher level of abstraction. Semantic web service, the combination of semantic web and web services, can make the automatic discovery, composition, execution, and monitoring of web services reality.This dissertation does a research on the automatic discovery and composition of semantic web services. We have designed and implemented a prototype system on the basis of automatic discovery and composition of semantic web services. In this dissertation the automatic service discovery refers to the automatic selection of services to meet users' preferences and constraints. And the automatic service composition refers to the automatic generation of the composite service to meet the user' demand. The main points of our work are described as follows:1. We present a semantic description model for web services to support the automatic service discovery and composition. The complet sermantic description model contains the following general types of information: the functional information, the service semantic information, non-functional information, and the description information of the data elements of service parameters.2. We present a method of automatic service discovery. In the method we firstly infer the initial state and required objective from the users' demand, and then contrast them with the semantic information of the preconditions and effects of advertised web services. The matching degree is determined according to a given algorithm.3. We propose a technique for the automated composition of web services. By the technique computers can understand the users' demand unambiguously, and then generate abstract workflows through semantic resoning according to the demand and the semantic information of the advertised web services. And the generated abstract workflows can be translated into executable processes, e.g., BPEL4WS after semantic transformation and heterogeneity elimination.4. We propose a model of process composition of web services on the basis of colored Petri Nets to validate the correctness and effectivity of the generated composite web services.