1,721,024 research outputs found
On the expressive power of movement and restriction in pure mobile ambients
No full textAbstractPure mobile ambients is a process calculus suitable to focus on issues related to mobility, abstracting away from aspects concerning process communication. However, it incorporates name restriction (i.e. the (νn) binder) and ambient movement (i.e. the in and out capabilities) that can be seen as characteristics adapted, or directly borrowed, from the tradition of communication-based process calculi. For this reason, we retain that it is worth to investigate whether or not these features can be removed from pure mobile ambients without losing expressive power.To this aim, we consider two variants of pure mobile ambients which differ in the way infinite processes can be defined; the former exploits process replication, while the latter is more general and permits recursive process definition. We analyse whether or not the elimination of ambient movement and/or name restriction reduces the expressive power of these two calculi, using the decidability of process termination as a yardstick. We prove that name restriction can be removed from both calculi without reducing the expressive power. On the other hand, the elimination of both ambient movement and name restriction strictly reduces the expressive power of both calculi. As far as the elimination of only ambient movement is concerned, we prove an interesting discrimination result: process termination is undecidable under recursive process definition, while it turns out to be decidable under process replication
Process discovery and Petri nets
No full textThe aim of the research domain known as process mining is to use process discovery to construct a process model as an abstract representation of event logs. The goal is to build a model (in terms of a Petri net) that can reproduce the logs under consideration, and does not allow different behaviours compared with those shown in the logs. In particular, process mining aims to verify the accuracy of the model design (represented as a Petri net), basically checking whether the same net can be rediscovered. However, the main mining methods proposed in the literature have some drawbacks: the classical α-algorithm is unable to rediscover various nets, while the region-based approach, which can mine them correctly, is too complex.
In this paper, we compare different approaches and propose some ideas to counter the weaknesses of the region-based approach
Comparing Truly Concurrent Semantics for Contextual Place/Transition Nets with Inhibitor and Read Arcs
No full textThe paper is centered around the study and comparison of truly concurrent semantics for P/T nets with inhibitor and read arcs (called henceforth contextual P/T nets). We start proposing a causal semantics for P/T nets, that we prove to be equivalent to history preserving bisimulation defined on nonsequential processes. Then we develop a conservative extension of the causal semantics to contextual P/T nets and we prove this one to be finer than step semantics. Finally, a comparison of causal semantics with the process based semantics for contextual P/T systems proposed in [7] is carried out
Synthesis of Nets with Inhibitor Arcs
No full textThe synthesis problem for Petri nets consists in the construction of a net system whose behaviour is specified by a given transition system. In this paper we deal with the synthesis of elementary net systems extended with inhibitor arcs, i.e. arcs that test for absence of tokens in a place. We characterize the class of transitions systems corresponding to the sequential execution of these nets, which is a proper extension of the one obtained by the execution of nets without inhibitor arcs. Finally, we try to minimize the number of inhibitor arcs; we look for conditions guaranteeing that an inhibitor arc is really used, i.e. its presence influences the behaviour of the net
Integrating TwoTowers and GreatSPN through a Compact Net Semantics
No full textStochastic process algebras (SPAs) and stochastic Petri nets (SPNs) are two well known formal methods for the functional and performance modeling and analysis of computer, communication and software systems. Starting from the mappings from process algebras to Petri nets proposed in the literature to provide a truly concurrent semantic framework to concurrent programming languages, in this paper we define a new SPN semantics for SPAs in order to facilitate the integration and the cross fertilization between the two formalisms. We then prove that our net semantics is correct via a retrievability result. Afterwards, we demonstrate that it improves on the previously proposed net semantics with respect to the size of the resulting SPNs and on the standard interleaving semantics because of the detection of system symmetries. Furthermore, we illustrate its usefulness by showing how to reinterpret at the SPA level the results efficiently obtainable at the SPN level. Finally, we describe the implementation of our net semantics that has been realized to integrate the EMPAgr based software tool TwoTowers with the GSPN based software tool GreatSPN
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