Approximate real-time decision making: Concepts and rough fuzzy Petri net models

This paper considers the construction of Petri nets to Simulate the computa tion performed by decision systems. Algorithms are given to construct Petri nets which correspond to decision rules, information systems, and real-tim e decision systems. Rough as well as rough fuzzy Petri net extensions of co lored and generalized fuzzy Petri nets are used to create highly parallel p rograms to simulate reasoning system computations. Constructed nets make it possible to evaluate the design of decision system tables, and to trace co mputations in rules derived from decision tables. Start places of nets are connected to Dill process receptors which await input from the environment. Time consumption during the propagation of outputs from sensors in a decis ion system is monitored with timers called approximate time windows, which measure durations between firings of decision transitions relative to time granules with names such as early, ontime, and late. Guards on decision tra nsitions are propositional functions which permit a rule to fire for some s ensor values and not for others. In addition, the design of guards makes al lowance for multivalued logic, where conditional sensor readings are assess ed in terms: of their degree of membership in sensor measurement granules. In some cases, a rule can fire if the degree of truth of its guard (premise ) is above some threshold. Through simulation, designers can arrive at reas onable estimates of the period of timers on decision transitions. The appro ach to simulating computations by decision systems presented in this paper results in fast, massively parallel programs implementable on a multiproces sor. (C) 1999 John Wiley & Sons, Inc.