基于颜色Petri网的网格服务组合

Grid Services Composition Based on Colored Petri Nets

在新的面向服务的网格计算架构下,网格服务为Internet上的分布式计算提供了一种重要范例。对服务提供者和消费者来说,通过组装已有网格服务来创建新的增值网格服务的应用模式已经出现。网格服务的组合已经成为网格研究领域中的一个重要课题。由于可用网格服务的复杂性,许多网格服务表现出复杂的会话协议,要求其提供的操作能根据特定的规则进行调用。讨论了以下几个问题:(1)如何精确描述网格服务的会话协议;(2)如何建立组合规则来对选定的组件服务进行合成;(3)如何验证整个网格服务组合的正确性,尤其是被合并的组件服务的一致性和它们的会话协议。Petri网提供了描述并发系统同步的结构,高级编程语言提供了描述和操作数据值的结构,而颜色Petri网结合了Petri网和高级编程语言的表达能力。为了解决上述问题,提出了一个基于颜色Petri网的会话协议和网格服务组合模型,其使用颜色Petri网的带颜色的token来模拟业务流程的不同消息和事件类型,把服务的会话协议和网格服务组合过程转换为颜色Petri网(CPN),利用现有的CPN的专门工具(如CPN Tools)来对CPN进行模拟以分析评价系统的性能和行为性质。

Under the new service-oriented grid computing architecture,grid services offer a prominent paradigm for dis- tributed computing on the Internet. It is an emerging opportunity for both service providers and service consumers to create the value-added service by assembling new, value-added grid service out of existing ones. grid services composi- tion has become an important research issue in Grid field. As the complexity of the available Grid services, many of them exhibit complex session protocols, requiring that the offered operations are invoked according to specific rules. This pa- per addressed the problems： （1） how to specify complex session protocols of grid service, （2） how to construct compo- sition rules to composite component service, and （3） how to verify grid services composition, especially its conformance to component services＇ session protocols. Petri net provides the constructions for specifying synchronization of concur- rent processes,and the programming language provides the constructions for specifying and manipulating data values, while colored Petri net （CPN for short） combines the strengths of Petri net with the expressive power of high-level pro- gramming language. In order to address the above problems, we proposed a CPN-based model for the specification of both the session protocol and the composition of grid services. Through using the colored token of CPN to model diffe- rent message and event type of business process, we can transform services session protocols and grid service composi- tion process into CPN, then analyze and evaluate behavioral properties and performance of the system by CPN Tool, an available specific tool for CPN.