中文摘要：

在工作流网、开放网等Petri网模型的基础上，提出适合描述面向服务系统的Petri网模型-EON（扩展开放网）．针对服务的各种组合方式定义了五种EON的组合算子，利用这些组合算子可以从基本EON组合成复杂EON．基于这些组合算子，EON本身可以采用代数化的构造性方式表达，本文进一步给出EON的结构化操作语义，这种语义是遗忘式的，不依赖于EON的标识，而是用发生变化的代数表达式描述EON的运行状态．

英文摘要：

A Petri net model - EON （Extended open net ） suited for service oriented system modeling were presented based on the workflow petri net （ WF_Net ） and opent net. Five composition operators were defined for the different composition style of service o- riented systems. Complex services can be constructed from simple ones use those composition operators. Based on those composition operators, an EON can be described by algebraic expressions constructively. A structural operational semantics for EON were defined which didn＇t rely on the mark of nets. The state of EON can be represented by algebraic expressions too.