Research And Application On QoS-based Grid Service Composition And Optimization

Currently Grid is a trend in parallel and distributed processing technology,whose goal is to share massive heterogeneous resources in network.OGSA(Open Grid Service Architecture) is the standard of Grid Architecture actually and it abstracts all distributed resources into standardized Grid Services.Nowadays,Grid applications are more and more complicated and many of them are composed by a set of grid services.Therefore,Grid Service Composition is an issue for us and its goal is to reduce the manual intervention in services finding,selecting and composing.Otherwise,Users focus on the QoS(Quality of Service) of Grid Service other than their functions.Firstly,this thesis provides a novel QoS model for Grid Service Composition,which includes definition of the QoS of single service and the formulas to compute the QoS of composite service.Secondly,this thesis proposes an automatic service composition method based on annotated dependency graph which considers both services' input/output and pre-condition/post-condition.It gets service dependency graph by means of searching service composition path based on service request and then transforms service dependency graph into a structured process model.Thirdly,this thesis applies the grid services composition and optimization approach to slove the problem of grid services selection and designs a QoS global optimal model which can satisfy the user constraints.Then it adopts ant colony algorithm and genetic algorithm to resolve the optimization problem respecttively.Finally,this thesis designs the system of grid service composition and optimization based on grid portal.