The use of High-Level Petri Nets for developing executable architectures, and simulations of these architectures, has become increasingly more accepted over the past decade for several reasons: they are based upon formal mathematics that provides proven methods for their verification; they are relatively easy to learn and use; they can be used to describe asynchronous concurrent systems; they are supported by tools that simplify the process of composing and executing them. However, Petri Nets, as originally formulated in the early 1960s, did not include the concept of time. Since then, several extensions of the basic Petri Net methodology have developed to address timing; however, none meets all of the requirements for describing complex military and commercial architectures. The proposed investigation will identify a comprehensive methodology for describing timing and provide a strategy for implementing it in an executable architecture tool. Two specific timing problems will be addressed. Architectures that integrate communications and operations are difficult to describe and execute because these components evolve on significantly different time scales; therefore, a mixed-time resolution strategy is required. Many systems and operations are better described as continuous rather than discrete process, and thus cannot be well described by the current generation of tools.
Keywords: High-Level Petri Nets, Continuous Event Simulations, Executable Architecture, Discrete Event Simulations, Hybrid Petri Nets, Colored Petri Nets, Timed
