Research On Key Technologies Of Service Grid For Parallel And Distributed Simulations

Large scale parallel and distributed simulations require a multitude of resources and collaboration between simulation participants. Grid can enable resource sharing and collaborative problem solving across multiple organizations, so it provides an efficient way for large scale parallel and distributed simulations. And currently, grid technology is developing towards Service Oriented Architecture, and provides varieties of functions to grid users through services in order to guarantee the loose coupling of functional modules of grid and their interoperability in heterogeneous environments. To support the fulfillment of large scale parallel and distributed simulations, it is possible to construct the service grid for parallel and distributed simulations by providing a set of standard services, ultimately to enable the sharing of simulation relevant resources and the achievement of collaborative simulations.The dissertation firstly described the application scenario of the service grid for parallel and distributed simulations, and identified the key services and functions that the service grid must provide, through demand analysis. These key services and functions included High Level Architecture(HLA) Runtime Infrastructure(RTI) service, resource discovery service, simulation execution service, and simulation task migration. Then on the basis of the research on relevant technologies, the overall framework of the service grid for parallel and distributed simulations was determined. It clarified the hierarchy of the service grid, which was composed of resource level, simulation basic service level, simulation core service level, simulation portal level, as well as user level.Service enabling of HLA RTI was indispensable to provide RTI service in the service grid. The difference of interoperability between HLA in military domain and Web service in commercial domain was analyzed. And afterwards, the concept of HLA RTI's service enabling and its concrete methods were also given. As an emphasis, the key problem and possible solutions of service enabling of HLA RTI were discussed, in terms of the definition of Web Service interface for HLA RTI, message encoding and decoding, invoking status maintenance, RTI deploy pattern, etc. Based on the solutions of these problems, an approach to web enabling HLA RTI and its implementation based on Globus Toolkit were given. In addition, the problem of federates'web service enabling and its solutions were discussed.The discovery service was indispensable for the service grid to enable resource discovery in grid environment. The resource description was prerequisite for the resource discovery. This dissertation proposed a semantics-based resource description method and corresponding resource matching methods. This method constructed relevant domain ontology for resource description at first, and then used the concepts and relations defined in this ontology to describe the resource; therefore the semantics were introduced for the resource description. As a result, inaccuracy and incompleteness that resulted from semantics shortage were fixed. After constructing the resource description, a discovery service with the ability of auto-organization was proposed. It facilitated management and usage of the service grid, and surmounted performance neck and single fault point that implicitly existed in centralized resource discovery systems.Service quality assurance was one of the main characteristics that distinguished the Grid technology from other distributed computing technologies. The service grid needed to provide load balance mechanism for parallel and distributed simulation's execution in grid environments. Simulation task migration was one of main measures to achieve load balance. The studies clarified general migration issue, emphasized on migration protocols and methods for HLA based simulations, and proposed a federate migration method based on mobile agent. And eventually, the load of HLA based simulations was balanced, and promoted the execution efficiency of parallel and distributed simulation in grid environment, through the said method.Computing resources was one kind of most important resources in the service grid, and was also the most requisite for large scale parallel and distributed simulations. The service grid must support the job of large scale parallel and distributed simulations to run on these multitudes of computing resources. The management and scheduling algorithm of simulation jobs were researched. Based on the research, a simulation execution management service was designed as one important part of the service grid. As a supplement for the simulation execution management service, the simulation basic execution service was designed and further it is discussed how to encapsulate local computing resource as simulation basic execution service.Based on the proposed overall framework and key technology, a prototype system was designed and implemented. And significantly, it was validated that the above-mentioned key technologies were feasible to fulfill the sharing of simulation resources and supporting the achievement of collaborative simulation, under a typical scenario of some simulations confront system.