中文摘要：

进程代数是一种适合描述Web服务组合的形式建模语言,然而同样对QoS建模和分析的支持不足.在现有进程代数的基础上,提出了一种代价概率进程代数PPPA（priced probabilistic process algebra）,给出其语法和语义,证明其具有功能、概率和代价的统一建模和分析能力.给出了基于PPPA统一建模和分析Web服务组合功能和QoS的方法.实例建模和分析了Web服务组合的功能、可靠性、性能和代价,其结果表明,PPPA可以有效地支持Web服务组合功能和QoS的形式化统一建模和分析.

英文摘要：

This paper proposes a process algebra called PPPA（priced probabilistic process algebra） by extending an existing process algebra with QoS modeling capability.This paper presents its syntax and semantics to prove that it can model not only functionality,but also non-functionality,such as reliability,performance,and cost.Finally,this paper moves to model and analyze both functionality and QoS of Web services composition in a united way based on PPPA.The paper illustrates the effectiveness with an example to prove that PPPA can support formal modeling and analyzation of QoS of web services composition