Petri net

About: Petri net is a research topic. Over the lifetime, 25039 publications have been published within this topic receiving 406994 citations.

A divide-and-conquer-method for the synthesis of liveness enforcing supervisors for flexible manufacturing systems

Abstract: In this paper a divide-and-conquer-method for the synthesis of liveness enforcing supervisors (LES) for flexible manufacturing systems (FMS) is proposed. Given the Petri net model (PNM) of an FMS prone to deadlocks, it aims to synthesize a live controlled Petri net system. For complex systems, the use of reachability graph (RG) based deadlock prevention methods is a challenging problem, as the RG of a PNM easily becomes unmanageable. To obtain the LESs from a large PNM is usually intractable. In this paper, to ease this problem the PNM of a system is divided into small connected subnets. Each connected subnet prone to deadlocks is then used to compute the LES for the original PNM. Starting from the simplest subnet prone to deadlocks to make the subnet live, monitors (control places) are computed. The RG of each subnet is considered and split into a dead-zone (DZ) and a live-zone. All states in the DZ are prevented from being reached by means of a well-established invariant-based control method. Next, the computation of monitors is followed for bigger subnets. Previously computed monitors are included within the bigger subnets based on a criterion. This process keeps the DZ of the bigger subnets smaller compared with the original uncontrolled subnets. When all subnets are live we obtain a set of monitors that are included within the PNM to obtain a partially controlled PNM (pCPNM). A new set of monitors is also computed for the pCPNM. Finally, a live controlled Petri net system is obtained. The proposed method is generally applicable, easy to use, effective and straightforward although its off-line computation is of exponential complexity in theory. Its use for FMS control guarantees deadlock-free operation and high performance in terms of resource utilization and system throughput. Two FMS deadlock problems from the literature are used to illustrate the applicability and the effectiveness of the proposed method.

Decidability of a temporal logic problem for petri nets

Abstract: The paper solves an open problem from [4] by showing a decision algorithm for a temporal logic language L ( Q ′, GF). It implies the decidability of the problem of the existence of an infinite weakly fair occurence sequence for a given Petri net; thereby an open problem from [2] is solved.

B(PN)2 - a Basic Petri Net Programming Notation

Abstract: This paper presents the syntax of a concurrent programming notation which integrates a variety of process interaction techniques, its compositional Petri net semantics via the Box calculus, and an example of using the semantics for program verification.

A semantics for every GSPN

Abstract: Generalised Stochastic Petri Nets (GSPNs) are a popular modelling formalism for performance and dependability analysis. Their semantics is traditionally associated to continuous-time Markov chains (CTMCs), enabling the use of standard CTMC analysis algorithms and software tools. Due to ambiguities in the semantic interpretation of confused GSPNs, this analysis strand is however restricted to nets that do not exhibit non-determinism, the so-called well-defined nets. This paper defines a simple semantics for everyGSPN. No restrictions are imposed on the presence of confusions. Immediate transitions may be weighted but are not required to be. Cycles of immediate transitions are admitted too. The semantics is defined using a non-deterministic variant of CTMCs, referred to as Markov automata. We prove that for well-defined bounded nets, our semantics is weak bisimulation equivalent to the existing CTMC semantics. Finally, we briefly indicate how every bounded GSPN can be quantitatively assessed.

Validation and verification of software process models

Abstract: We introduce a software process modeling language — called FUNSOFT nets — which has a formally defined semantics in terms of Predicate/Transition nets. For this language we have implemented various analysis facilities. We point out which benefits can be gained from a thorough software process model analysis. We explain how software process models can be validated and how software process model properties can be verified. The proposed software process model validation is based on software process simulation, the proposed verification of software process model properties is based on well-known Petri net algorithms and on the notion of quantity restricted coverability trees. Finally, we explain how the proposed analysis facilities are implemented in the analysis tool ANAMEL, which is embedded into the software process management environment MELMAC.