JXTA Based Parallel Service Invocation Model for Peer to Peer Web Service Composition

Abstract

Web Services are being hailed as a solution to many of the problems of distributed computing. When numerous web services are available it seems natural to reuse existing web services to create composite web service. A pivotal problem of web service composition is how to model input and output data dependencies of candidate web services to form composite web services efficiently. In a sequential web services composition model each web service needs to wait till the previous web service provides its output for the web service to be invoked, even if they don’t have any inter dependency. Hence they are very poor in resource utilization. P2P (or peer-to-peer) networking is a network model where, depending on an operation's context, any node can operate as either a server or a client. P2P provides certain interesting capabilities such as fault tolerance, high scalability which are not possible in traditional client/server networks. JXTA holds tremendous promise for the P2P world. It defines a set of protocols that developers can use to build almost any P2P application. JXTA-SOAP and “peer to peer web services architecture based on Mocha” are two web service architectures which reflect all the powerful features of p2p computing. But the limiting factor is both of these models invoke web services strictly in a sequential pattern and JXTA has no way to invoke composite web services. Business applications like banking systems, weather services which involve image processing tasks require a constantly growing number of large data transactions and data processing capabilities. For P2P applications which perform a lot of web service transactions, the use of sequential service invocation architecture may become a limiting factor. During the study attempt is made to introduce Parallel Service Invocation model and Web Service composition model to JXTA. The model is implemented by using Java, XML RPC, AXIS2, JXTA and JXTA-SOAP technologies. XML Tree based notation is introduced to represent composite web service in JXTA environment. Parallel service invocation plan is tested with sequential version and clearly observed efficiency improvement.