A Class of Petri Nets for Modular and Hierarchical System Modeling

Existed researches on transition refinement and subnet abstraction mainly paid attention to preserve different attributes during the transformation, usually led to very strict conditions for the subnet. Aiming to provide the same service and interface after transformation as original module while less restricts are given, a kind of subnet - the Engineering Subnet, is put forward to model complex manufacturing system. The surrounding environment and interface of a subnet are analyzed and defined, the concept "standardized interface" is presented; transition subnets are classified into different types, the idea of "normalized subnet" is presented; a live and normalized subnet with finite live loopbacks is proved to be an Engineering Subnet. Because of live loopbacks owned by Engineering Subnets, the same interface and service as the original module are reserved after the transformation between an Engineering Subnet and the corresponding transition, mean while fewer preconditions are required for the Engineering Subnet compared with previous researches.