Timed petri nets in modeling and analysis of concurrent systems

本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，某些事件可以同时发生的系统，但这些事件的发生顺序和频率有限制。多处理器和分布式系统、数据库系统、通信协议和网络是这样的系统的示例。由于Petri网非常简单的表示并发和事件同步，它在并发系统的建模和分析中得到了广泛的应用。为了考虑建模活动的持续时间，并使用相同的模型对建模系统进行定性和定量分析，已经提出了几种类型的“带时间”Petri网。然而，现实生活中的系统的网络模型往往是太复杂，太难以直接处理（所谓的“状态爆炸问题”的状态为基础的模型）。因此，需要特殊的技术（和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）从建模系统的规范自动（或半自动）导出网络模型，（ii）导出模型的有效分析方法，以及（iii）开发用于生成、分析和评估网络模型的软件工具。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（这将隐藏Petri网的更先进的方面）将增加Petri网在复杂系统的建模，分析和评估的普及。

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.