On Specification Informatics in Discrete-event Systems - State-transparency for Clarity of Finite Automata as Control Specifications

In control of discrete-event systems (DES’s), the formalization of control requirements from natural language statements is essentially a human endeavor. Without automated support tools, human designers often face the uncertainty of not knowing if the control requirements formalized in the rudimentary DES formalism of automata are as intended, motivating the automata-theoretic study of specification informatics in the field of DES’s. A specification automaton that renders its linguistic description more transparent should help designers ascertain the prescribed requirement. Such transparency may be formalized in either the state space or the event space of the DES. In this paper, treating the former as fundamental, a state-transparent specification automaton is conceptualized with respect to a full specification automaton (‘full’ in the sense of having all the a priori transitional constraints of the DES embedded in it). It contains only specification relevant states called specification epochs. Each epoch denotes a “well-defined” disjoint subset of states of the full specification automaton in the same phase of execution, meaningfully aggregated such that the resultant specification automaton retains the original restrictiveness on the DES. The problem of maximizing the state-transparency of specification automata for DES’s is then theoretically formulated. Subject to human perceptive or cognition limits, we believe that such a maximally state-transparent specification automaton could be more comprehensible, showing clearly the compliant execution of the system through a minimum number of specification epochs, and should aid designers in clarifying if the requirement prescribed is the one intended.