Discussion on: Supervisory control of discrete event systems with flexible marking

This paper proposes a new class of Discrete Event Systems endowed with control called DES with flexible marking (DESFM). The DESFM is modeled by a language and a control structure. The language contains all the strings of events that the system can generate. The control structure is a function that associates a set of controls to each string generated by the system. A control encapsulates information of event-enabling and marking for the string. The model is shown to be suitable for systems with abstraction for hierarchical control. The condition for existence of a supervisor and the synthesis of an optimal supervisory control scheme, in the sense of maximal permissiveness, are given. An illustrative example where the DESFM is naturally applied is presented