Controller design and implementation: An approach based on problem frames and Petri Net models

Petri nets are often used as a design tool amenable to model specification, simulation, and verification. They are typically used in the design phase often with no clear connection to the requirements phase, including requirements specification. This paper shows how a class of non-autonomous Petri Nets can be used as an executable model for the design and implementation of machine domains in the context of the Problem Frames approach. This provides a requirements-design connection together with model simulation and verification. More specifically, Problem Frames are used to support requirements, problem and machine specifications amenable to a direct translation to IOPT nets, a class of non-autonomous Petri nets especially adapted for controller specifications. To that end, we propose a set of semi-formal rules for machine specifications in problem frames, which take advantage of the concepts available in IOPT nets, namely input and output signals and events, states, and a net composition operation. We illustrate the approach using an example.