Research And Realization On Web Services Composition

The Internet is now undergoing an evolution from a simple platform for information sharing to an open sharing distributed computing infrastructure. With more and more data resources, computing resources and applications accessible via the Internet for public usage, resource sharing and application integration across organizational and locational boundaries have been recognized as comprehensive requirements in many different domains, such as commerce, scientific research, military area and etc. In recent years, the concept of service has been proposed as a mean of wrapping and abstracting diverse resources in open web environment, with makes service composition the natural way for dynamic resource aggregation and flexible application integration.With the continuous application of Web services, Web services composition has triggered a considerable number of research efforts both in academic and in industry. Web services composition is the ability to create a new, more powerful Web services by incorporating some existing Web services together. This Web services composition technology will enable commercial, scientific research, military and other areas reuse the existing services when there is demand for the new system. So, this technology can avoid the duplicate development, impove the resource utilization and reduce the development costs. At present, many domestic and foreign research institutions has started research work with Web services composition technology, and have achieved some valuable exploratory. But, Web services composition areas such as calculation framework, model theory, key technology and implementation mechanism has many problems to be solved. This paper will deep into the approaches of web services composition.The environment of distributed, heterogeneous, multi-autonomous-fields and poor-robust WAN (wide area network), which is represented by Internet, requires Web services composition to satisfy higher demands. The algorithm of Web services composition should satisfy several requirements as follows:1. The dynamic changes of the runtime environment and user requirements desire that Dynamic Web service composition can break away from the static composition mode rectify itself and reduce the manners of manual work so that satisfy the dynamic characters of WAN and provide efficient, cheap service composition.2. Because of Internet resources is very rich, the number of Web services registered by the UDDI may be very huge, and should respond the composition result as quickly as possible, therefore, the algorithm of Web service composition should meet the efficiency requirements.3. According to the service request, the method should return the corresponding result of combination, and should be able to satisfy the service request, therefore, should ensure the correctness of the Web service composition algorithm.In this paper we will carry out the following tasks based on the analysis of the characteristics of the Web services composition approaches.1. State the concept of Web services and features, the details of the technical architecture of Web service, introduce the technical protocol that Web services depend on briefly. XML is mainly used for data representation, providing a standard data formatted representation method for data; SOAP use XML style, provices a simple, lightweight, used for the message framework of the exchange of the structured information in the distributed environment; WSDL is a XML language used for descripting Web services, provide the informations about the following areas: the functions of the Web service, how to access service and the location of Web service.UDDI defines a information model used for the registration and discovery of the service, in fact, it is the directory of Web services. Finally, analyse the weakness of the data standards, interface standards and the standardization of business process.2. Introduce the basic concepts and technologies of the Web services composition; classify the methods of Web service composition on the different standards, then classify and introduct the current representative method. On this basis, introduce several existing comparison standards, and compare typical algorithms with these standards.3. Introduce and analysis the service chain-based approach for Web service composition, find the shortcomings in the ability this method exist, this method can only deal with the general sequence combine relationship. But in actual, there may be several relationships between the services in the processes of Web services composition. In this paper, we do a simple overview and summary of the relationship between the Web services, find that there is three relationships between them. These three relationships is sequence, divergence and convergence, all the combinations of Web services can be achived by expanding and combining these three relationships, in despite of the situations of Web services combination may be very complexity in fact. On this basis,We improve the above mothod, proposed a service tuple chain-based approach for Web service composition.This method not only can deal with the general sequence relationships between the order of composition, but also can deal with complicated situations such as concurrency and convergence. This method does an extend on the service chain-based approach, extract service tuples from all the services registered on the UDDI, and treat the founded service tuples as Web services.After these, just apply the service chain-based approach on these treated Web services.4. Experiment the proposed approach using WSC 2007 and EEE 05 as the standard test data sets. In this procedure, in order to reduce the computation, we proposed a preprocessing strategy. Through experiments, after the preprocessing, the number of Web services has reduced about 90%, the number of input and output parameters reduced about 85% in WSC 2007 test situation; the number of Web services has reduced about 90%, the number of input and output paramenters reduced about 75-90% in EEE 05 test situation. We can find that the preproceeding procedure has reduced the amount of data on the combination operation, so reduce the computation, lay the foundation for the efficient of the algorithm. After that, we do experiments on the performance of algorithm using WSC 2007 as test dataset, through the analysis of experimental results; we found that this algorithm has a good flexibility and scalability in the performance of the algorithm. Then, do experimances on capacity using EEE 05, through the results, we found that the method proposed by this paper can not only deal with combinations of sequential relations, but also the other relations; Finally, do a comparation BF* and service chain based approach with the method we proposed using EEE05 as test dataset, proved that the algorithm we proposed has a relatively well capacity.5. Analyze and summarize the existing lacks of the algorithm, proposed the next possible focus.As stated above, this paper focused on the current methods of dynamic service combination, introduced a well performed, strong ability approach, has a great significance to promote research and application of Web services composition.