Systematic Approach for Composing Web Service using XML (original) (raw)
The internet has created the foundation for a networked economy-an extended business community in which vendors, partners, and customer interact and collaborate. Web Services are self-contained, self -describing, modular applications that can be published, located, and invoked across the web. One of the most important and promising advantages of Web service technology is the possibility of combining and linking existing services to create new web processes according to the given requirement. We shall present the motivation for web services Composition. Web Service is a software component invoked over the Web via an XML message that follows the Simple object Access Protocol (SOAP), which is a simple XML based protocol to let applications exchange information over HTTP and to transport the messages using open protocols standard. Web Services are based on distributed technology and provide standard means of interoperating between different software applications across and within organizational boundaries with the use of XML. Web services are provided with different Quality of Service (QOS) so they should be selected dynamically on composition. Optimized selection is achieved by minimizing a certain objective function. According to study of objective function, it should always be based on user requirements. We will introduce four types of objective function styles. Sometimes a single service given alone does not meet user's needs. In this case, it is necessary to compose several services in order to achieve the user's goal. This proposal discusses the Quality of Service (QOS) aware composition of web services. The work is based on the assumption that for each task in a workflow a set of alternative Web services with similar functionality is available and these web services have different QOS parameters and costs. This leads to the general optimization problem of how to select web services for each task so that the overall QOS and cost requirements of each composition are satisfied. Serviceoriented architecture (SOA) provides a scalable and flexible framework for service composition. Service composition algorithms play an important role in selecting services from different providers to reach desirable QoS levels according to the performance requirements of composite services, and improve customer satisfaction.
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