Some new results on the state liveness of open guidepath-based traffic systems

Guidepath-based traffic systems is a pertinent abstraction that has been used extensively by the Discrete Event Systems (DES) community for the study of the traffic dynamics that take place in the automated unit-load material handling systems (MHS) encountered in various production and distribution facilities. A particular problem that has drawn extensive attention in the DES-based investigation of these systems, is the preservation of the system "liveness"; i.e., the preservation of the ability of the system agents to complete successfully their currently allocated tasks and engage repeatedly to similar tasks in the future. The first part of this paper establishes that for a large subclass of the considered traffic systems, the preservation of their traffic liveness in a maximally permissive manner reduces to the observation of a particular property that must be possessed by the admitted traffic states. The second part of the paper provides some complexity analysis for assessing the aforementioned property on any given traffic state, under some further assumptions regarding the operation of the considered traffic systems and the structure of the traffic states under consideration.