Investigation On The Key Technology Of Distributed Simulation Based On Web Services

Along with the development of simulation requirements and corresponding technology, technology connotation and application pattern of modeling and simulation are extended and enriched continuously. Especially with the development of network technology, distributed simulation demands higher level of interoperability and reusability. Web Services, which is based on XML, is a new application model for decentralized computing; it can be invoked by standard network protocols, and has the abilities of self-description and self-inclusion; it is an effective mechanism for the data and service integration on the Web as well. Objectives of this dissertation are applying Web Services to extend HLA distributed simulation, exploring the key technology of distributed simulation based on Web Services, making simulation resources, federates and Run Time Infrastructure (RTI) reside as web services on a Wide Area Network (WAN), realizing dynamic and uniform management, permitting an end user to join federation/simulation on WAN or compose a new federation/simulation from a browser.Concentrating on HLA distributed simulation framework based on Web Services, the dissertation mainly investigates on distributed simulation run time infrastructure based on Web Services, simulation data collection service based on simulation temporal database, and heterogeneous datasource union search oriented to distributed simulation resource repository, etc. Generally, the main research points in this dissertation are as follows:After analyzing existent problems of traditional HLA distributed simulation about interoperability and reusability, we investigate on extending HLA distributed simulation with Web Services. HLA Distributed Simulation Model with Low Coupling (HDSM-LC) and HLA Distributed Simulation Framework based on Web Services (HDSF-WS) are proposed; the core modules in HDSF-WS, including simulation services registry, simulator service and run time infrastructure service etc, are designed in detail. Simulation process model based on HDSF-WS is provided. In the HDSF-WS, federates and run time infrastructure are residing as web services on a WAN; remote simulation end users are able to implement their simulation codes respectively, and compose nessesary simulation services and run time infrastructure services to construct a large-scale distributed simulation system with ease. The proposed framework fully supports dynamic discovery of simulation run time infrastructure and simulation model, can incorporate Web Services Resource Framework and Web Services security criterion, and has the potential to build a fully-featured distributed simulation system.After analyzing the design of RTI, Distributed Simulation Run Time Infrastructure based on Web Services (RTI-WS) is designed under the HDSF-WS, the prototype of pRTI-WS is developed, its conceptual feasibility is validated by application, and corresponding performance analysis and experimental tests are provided. The design framework of RTI-WS adds a SOAP/HTTP-based layer of RTI messaging proxy between federates and RTI, and with certain real time performance loss, RTI-WS can greatly upgrade the reusability and interoperability of HLA distributed simulation. RTI-WS is applicable for coarse-grained applications of distributed simulation on WAN.For the purpose of efficient data collection and real time query of distributed simulation systems, a simulation temporal database model is proposed, and the prototype of simulation temporal database is designed, including corresponding storage realization, index design, as well as query optimization. The prototype has the abilities of fast collecting and high efficient query. It is especially applicable for distributed simulation's data collection systems oriented to simulation replaying and real-time query.Analyzing the objectives of distributed simulation data collection, a method of distributed simulation temporal data collection is proposed based on Web Services. Combined with simulation temporal database, a distributed simulation data collection service is designed. Dynamic discovery and integration of data collection application is realized under the framework of HDSF-WS. Corresponding application instance and performance tests are provided subsequently.Aiming at the efficiency problems of simulation heterogeneous resources search and obtaining in distributed simulation resource repository, a framework of union search is design based on Web Services mechanism. Search Services Union Model, Result Record Metadata Model based on XML and corresponding algorithms are proposed for search services distribution and result fusion. After that, union search prototype is implemented, and performance tests are presented. Based on this design, union search system could be implemented simply and would have good space-time performance; it could unify heterogeneous data records by XML expediently and accomplish the global optimization by giving attention to character of every data source's search interface; it could achieve transparent integration to heterogeneous data sources' search interfaces, and improve availability of simulation resources.