OPNets : an object-oriented high-level petri net for real-time system modeling

Abstract

Real-time systems are usually characterized by complex, distributed and concurrent nature. They typically include a set of concurrent processes that operate asynchronously to accommodate the different speed requirements of various hardware devices. To model such a system in an elegant way, many tools and methodologies have been developed. Among them, Petri net has been found to be useful for modeling real-time systems since it provides elegant expressions for concurrent control structures and validation mechanisms. Petri net is abstract and formal model of information and control flow in systems exhibiting concurrency and asynchronous behaviour. It is very simple and natural in structure, yet quite powerful in modeling and analyzing such systems. However, the complexity of the net increases drastically as the size of the net grows, which is one of the main obstacles to apply Petri net model for large and complex real-time systems. In order to reduce the complexity of the net and hence to increase the maintainability and reusability of the developed model, we present an approach, called OPNets, for modeling real-time systems based on the object-oriented formalization of high level Petri nets. OPNets decompose a target system into concurrent objects and establish message-passing relations among them. With a view to reducing dependency among objects, the message-passing relations are designed such that each object is organized as independent as possible by decoupling the communication knowledge and separating synchronization constraints from the internal control structure of objects. To validate the overall system which is composed of the hierarchically organized objects and interconnection relations, tw0-step validation procedure is presented which reduces the complexity and computational efforts required. The analysis method validates each object in the first step and then globally checks the synchronization constraints among objects. As illustrations, a manufac...