Abstract: Workflow pattern is a basic part of the workflow model，and the synchronization machine of Petri nets is the most efficient method in workflow modeling.In this paper，common workflow patterns are categorize into 3 kinds：complete synchronization，competitive synchronization and non-synchronization.The synchronization machine of Petri nets is able to model the complete synchronization，however，not the competitive synchronization and non-synchronization.An extended synchronization machine is presented in this paper，with its capabilities of modeling all the patterns above.Compared to the original synchronization machine，the new one extends the capabilities of modeling the competitive synchronization and non-synchronization.

Key words: workflow modeling, workflow pattern, synchronization machine, synchronic distances

摘要： 工作流模式建模是工作流模型的基础，Petri网同步器是目前最有效的工作流模型建模方法。使用网和同步距离对工作流模式进行分析，将目前常用的工作流模式归纳成为三种：完全同步、竞争同步、非同步。而Petri网同步器只能表示完全同步，不能表示竞争同步和非同步，为此提出一种改进的同步器，通过改进同步类型，使得同步器可以建模三种同步模式，较之改进前的同步器，增强了建模竞争同步模式和非同步模式的能力。

关键词: 工作流建模, 工作流模式, 同步器, 同步距离