Timed petri nets in modeling and analysis of concurrent systems

这项研究的长期目标是开发有效的方法来建模和分析并发系统，即一些事件可以同时发生，但这些事件发生的优先级和频率受到限制的系统。多处理器和分布式系统、数据库系统、通信协议和网络都是此类系统的例子。由于非常简单地表示并发性和事件同步，Petri网在并发系统的建模和分析中越来越受欢迎。已经提出了几种“随时间”的Petri网，以便考虑到模拟活动的持续时间，并使用相同的模型对模拟系统进行定性和定量分析。然而，现实系统的网络模型往往过于复杂和难以直接处理（基于状态的模型的所谓“状态爆炸问题”）。因此，需要特殊的技术（以及实现这些技术的软件工具）来分析许多现实模型。该项目的短期目标包括：(i)从建模系统的规格中自动（或半自动）推导出净模型，（ii）对衍生模型的有效分析方法，以及（iii）开发用于生成、分析和评估净模型的软件工具。所有这些目标都是互补的，因为它们涉及建模和分析过程的不同阶段。预计更有效的算法，特别是更用户友好的软件工具（将隐藏Petri网更高级的方面）将增加Petri网在复杂系统建模，分析和评估中的普及。

The long-term objective of this research is the development of efficient methods for modeling and analysis of concurrent systems, i.e., systems in which some events can occur concurrently but there are restrictions of precedence and frequency of such occurrences. Multiprocessor and distributed systems, database systems, communications protocols and networks are examples of such systems. Because of very simple representation of concurrency and synchronization of events, Petri nets have been gaining popularity in modeling and analysis of concurrent systems. Several types of Petri nets "with time" have been proposed on order to take into account the durations of modeled activities, and to use the same models for qualitative and well as quantitative analyses of the modeled systems. However, net models of real-life systems tend to be too complex and too difficult to be dealt with directly (the so called "state explosion problem" of state-based models). Therefore special techniques (and software tools implementing these techniques) are needed for analysis of many realistic models. Short-term objectives of this project include: (i) automatic (or semi-automatic) derivation of net models from specifications of the modeled systems, (ii) efficient analysis methods of derived models, and (iii) development of software tools for generation, analysis and evaluation of net models. All these objectives are complementary in the sense that they refer to different stages of the modeling and analysis process. It is expected that more efficient algorithms and, especially, more user--friendly software tools (which will hide the more advanced aspects of Petri nets) will increase popularity of Petri nets in modeling, analysis and evaluation of complex systems.