The Study And Implementation Of Heuristic Algorithm For Services Composition

Web services are self-contained modular business applications that have openInternet-oriented and standards-based interfaces. It provides a better solution for theinteroperability and integration of heterogeneous applications under loose-coupledenvironment. Web services technology is quite promising for the integration of businessapplications and service composition. Web services are more coarse-grained and operate ata higher level of abstraction.Internet has a lot of Web Service we can access,but most ofthem are in the state of isolation. Each of them has its own function, little relationship withothers. Single Web Service can only provide limited function, it can not fulfill complexbusiness requirements,it is necessary to compose several elementary Web Services. Thecomplex webserviceismadeofthewebservice components andtheelement webservices.Web service composition offers a simple way for the creation of complex applications. SoWeb Services Composition technology has become a hot research topic. Web ServicesComposition is one of important researches of Web Services. Web Services Compositionprincipal research problems are Web Services Composition Modeling, Web serviceCompositionVerifying,executingofcompositewebserviceandsoon.As the infrastructure is complex, there are many factors to influence the QoS of Webservices. Changes in traffic patterns, denial-of-service attacks and the effects ofinfrastructurefailures, lowperformanceofWebprotocols, andsecurityissues overtheWebcreate a need for Internet QoS standards. Often, unresolved QoS issues cause criticaltransactional applications to suffer from unacceptable levels of performance degradation,and it is skeptical if Web services can be employed to key application. Thus it is urgent toresearching QoS of Web Services. How to create robust service compositions becomes thenext step work in web services and has attracted a lot of researches.At the same time,webservices selection supporting global QoS constraints plays an important role in web servicescomposition. Nowadays, manyresearch institutions home and abroad have conducted quitea few researches on QoS and Web Services composition, and have made some valuableexploratory achievements. For example, how to make the estimation of QoS based on user preferences, how to validate and test in order to make the Web Service correct, and how tochoose the quality-driven services composition scheme and services composition based ontheQoSrequirements.The goal of service selection is selecting the most appropriate service based on therequirements from service consumers, which is an important part in the process of using aservice. However, with the prevailing of Web Services, the number of services on theInternet has been larger and larger. How to select a ser of services among large body ofservices with the same function in order to make the Composite Service achieve betterperformanceandbetterqualityisahotissueinrecentresearch.Currently,researchersoftheworld have made some valuable achievements on Web services composition; however,many other key technologies are to be further researched. But as a new field of study, newresearch issues keep emerging.The main contribution of this paper has the following two aspects:1) Optimization of community-based Web services management mechanism. In adynamic environment of network, if there are a large number of services which are similarin functional property, and different in non-functional properties with each other, so thatthere are too many service options, to find the most appropriate service form such a largescale selection of alternative services, portfolio of services will increase the engine load,and the computation of service selection module will be significantly expanded too. Thecalculation of similarity, can make the same or similar property web registration serviceregisterinthesameregistercenter.Thatis,WebServicesCommunity.In this paper, A hash mechanism is introduced at the basis of the community-basedmanagement mechanism. Hash mechanism introduced is essentially to do stratificationprocessing based on the basic services. Stratification is based on non-functional propertyregistered in the community, such as time, price, reliability, availability, credibility, etc. Ahash index table is set up for each basic services registered in the community. When a newbasic service is registered into this community, system will calculate each value ofnon-functional property according to the given hash function, And the information of newregistered basic services will be added into the corresponding layer. This will giveassurance that the first basic service found by combinational search engine is the localoptimal solution at the community's basic services. While a valid basis was founded for theadjustments of the follow-up basic service, the basis for the inspiration of the pruningstrategy is provided too. Experiments show that the given community managementmechanisms andtheintroductionofHash mechanism canimprovethesearch efficiencyfor theselectionintheservicecombination.2)Give a heuristic algorithm. For the activity of the combination of services, if theactivity number and the candidates set are relatively small, the package can be calculatedthroughthesimpleimplementationoftheenumeration,butasthescaleofactivitycontinuesto expand, the search efficiencywill be the bottleneck, especiallyfor those application whofrequentlydoselectionsofcombinationsolutions.In this paper, A heuristic service selected algorithm satisfied the user preferences isintroduced. The introduction of Community-based management techniques, reduced thesearch space of the service for the combination engine, directly improve the efficiency ofthe search. Combination of engine will decompose requested information entered by theuser, the decomposed information requested constitutes of several basic services, so thateachindividual will beabletoput basicservices fortargetedinformationat therequest ofacommunity on the search space. In this paper, by the calculation model QoS forCombination Service, after the introduction of hash mechanism for the communitymanagement of Web Services, based on a user preference to meet the combination ofefficientheuristicalgorithm.Thealgorithmcanenhancereusabilityoftheexistingportfolioof successful Web Services, reduce the cost of combination of Web Services, And webservices'accuracy and efficiency will be improved, while small search space, lowcomplexityand highspeed,abilitytodeal witha singleaim and goal ofmanyuser requestscan be supported. Simulation experiments show that solving it with the exhaustive searchresultsisveryclose,butitsratewasgreatlyenhancedtosolve.