多媒体同步是多媒体应用的一个重要需求。本文对OCPN模型进行了扩展，提出了一种基于时间Petri网的多媒体同步模型XOPCN，以对具有时间约束关系的多媒体合成进行规范描述，并具有支持灵活用户交互的能力。文中给出了处理异步用户交互的算法，并用示例说明。

Multimedia synchronization is a significant requirement for distributed multimedia applications.In this paper,we augment the OCPN model,and present a new multimedia synchronization model XOCPN based on timed Petri nets. Using this model we can give the formal specification for multimedia object compositions with time-constrained relations and deal with flexible user interaction. Algorithms for asynchronous user interactions are also presented, and explained by an example.