A Petri net, also called a place-transition net, is a mathematical representation of concurrent systems--systems in which an activity of one component of the system can occur simultaneously with other component activities. Modeling of a system based on a Petri net can reveal information about the structure and behavior of that system.

Examples of concurrent systems are the dynamic structure of an atom, high-speed computers, air traffic control systems, chemical reactions, and economic systems. In a computer system, for example, peripheral devices, such as printers and tape drives may operate concurrently under the master control of the computer. In an economic system, manufacturers may be producing some products while retailers are selling other products, and customers are using still other products, all at the same time. In such concurrent systems, each component can be described independently of the other components, although interaction of the components is...