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超媒体建模研究是当前一个重要研究方向。基于Petri网理论的模型是对有向图模型的改进,与其他模型比较,能够更好地刻画超媒体系统。原因如下:Petri网是一个二部有向图,适合于说明超媒体的链接机制;Petri网是一种天然的具有并行执行语义的自动机,模型可以自然地表达超媒体系统中的动态执行语义;Petri网能够说明各种顺序、并发和同步活动,满足描述多媒体表现的需要;利用Petri网的图形特性和严格的数学基础,人们可以检查和分析超媒体中的潜在问题。该文着重对四个典型的基于Petri网的超媒体模型:MHPN、HCPN、MORENA和HTSPN模型进行分析和比较。
Hypermedia modeling research is currently an important research direction. The model based on Petri net theory is an improvement on the directed graph model, which can better describe the hypermedia system compared with other models. The reason is as follows: Petri net is a two-part directed graph, which is suitable for describing the hyperlink mechanism. Petri net is a natural automaton with parallel execution semantics. The model can naturally express the dynamic execution semantics in hypermedia system ; Petri nets illustrate the sequence, concurrency, and synchronization activities needed to describe multimedia performance; Petri nets can be used to examine and analyze potential problems in hypermedia using the graphical nature of Petri nets and their rigorous mathematical foundations. This paper focuses on four typical Petri net-based hypermedia models: MHPN, HCPN, MORENA and HTSPN models for analysis and comparison.