Abstract: To make a service-oriented system dynamically adapt to its changing environment and requirement, it often needs to update some of its member services at runtime without wholly shutting it down. However, in order to ensure the consistency of the system, a member service can only be updated when it is in a safe state. In this paper, it studies the dependences between WS-BPEL（Web Service Business Process Execution Language） processes and their partners, which are used to predict the safe time points for dynamic updates. The experiment shows that the algorithm can help to update services in a low-disruptive way and without any compromise on system consistency.

Key words: on-line evolving, dynamic update, Web Service Business Process Execution Language（WS-BPEL）, dependency

摘要： 构件和服务等软件实体的动态更新是支撑软件系统在线演化的关键技术，该技术可以在不中断系统运行的前提下对软件系统的结构或行为进行调整。然而，为保证更新前后系统行为的一致性，只有当软件实体处于安全状态时方可进行更新。以基于WS-BPEL（Web Service Business Process Execution Language）的软件系统为例，通过分析WS-BPEL过程与其成员服务间的依赖关系，提出了一种可预判成员服务是否动态更新的算法。实验结果表明，依赖分析算法可以有效预判成员服务可动态更新的时机，从而在不影响系统行为一致性的前提下有效减少动态更新所引起的服务中断。

关键词: 在线演化, 动态更新, Web服务业务流程执行语言（WS-BPEL）, 依赖