arXiv subjects

Paolo Baldan

Publications and source records attributed to Paolo Baldan.

21 records · Page 2Linked to original sources

arXiv2014

Reduction of Event Structures under History Preserving Bisimulation

Event structures represent concurrent processes in terms of events and dependencies between events modelling behavioural relations like causality and conflict. Since the introduction of prime event structures, many variants of event structures have been proposed with different behavioural relations and, hence, with differences in their expressive power. One of the possible benefits of using a more expressive event structure is that of having a more compact representation for the same behaviour when considering the number of events used in a prime event structure. Therefore, this article addresses the problem of reducing the size of an event structure while preserving behaviour under a well-known notion of equivalence, namely history preserving bisimulation. In particular, we investigate this problem on two generalisations of the prime event structures. The first one, known as asymmetric event structure, relies on a asymmetric form of the conflict relation. The second one, known as flow event structure, supports a form of disjunctive causality. More specifically, we describe the conditions under which a set of events in an event structure can be folded into a single event while preserving the original behaviour. The successive application of this folding operation leads to a minimal size event structure. However, the order on which the folding operation is applied may lead to different minimal size event structures. The latter has a negative implication on the potential use of a minimal size event structure as a canonical representation for behaviour.

cs.LO↗

arXiv2014

A Logic for True Concurrency

We propose a logic for true concurrency whose formulae predicate about events in computations and their causal dependencies. The induced logical equivalence is hereditary history preserving bisimilarity, and fragments of the logic can be identified which correspond to other true concurrent behavioural equivalences in the literature: step, pomset and history preserving bisimilarity. Standard Hennessy-Milner logic, and thus (interleaving) bisimilarity, is also recovered as a fragment. We also propose an extension of the logic with fixpoint operators, thus allowing to describe causal and concurrency properties of infinite computations. We believe that this work contributes to a rational presentation of the true concurrent spectrum and to a deeper understanding of the relations between the involved behavioural equivalences.

cs.LO↗

arXiv2008

Bisimilarity and Behaviour-Preserving Reconfigurations of Open Petri Nets

We propose a framework for the specification of behaviour-preserving reconfigurations of systems modelled as Petri nets. The framework is based on open nets, a mild generalisation of ordinary Place/Transition nets suited to model open systems which might interact with the surrounding environment and endowed with a colimit-based composition operation. We show that natural notions of bisimilarity over open nets are congruences with respect to the composition operation. The considered behavioural equivalences differ for the choice of the observations, which can be single firings or parallel steps. Additionally, we consider weak forms of such equivalences, arising in the presence of unobservable actions. We also provide an up-to technique for facilitating bisimilarity proofs. The theory is used to identify suitable classes of reconfiguration rules (in the double-pushout approach to rewriting) whose application preserves the observational semantics of the net.

cs.LO↗