Visualisation and analysis of complex behaviours using structured occurrence nets

PhD ThesisA complex evolving system consists of a large number of sub-systems which may proceed concurrently and interact with each other or with the external environment, while its behaviour is subject to modification by other systems. Structured occurrence nets (sons) are a Petri net based formalism for modelling the behaviour of complex evolving systems. The concept extends that of occurrence nets, a formalism that can be used to record causality and concurrency information concerning a single execution of a system. In sons, multiple occurrence nets are combined using various types of relationships in order to represent dependencies between communicating and evolving sub-systems. The work presented in this thesis aims to develop a tool and extend existing methodology for structured representations of the behaviours of complex evolving system. The theoretical development focuses on the extension of existing son concepts. It addresses the issue of efficient son model checking and simulation, representations of alternative behaviour and time information, structuring son-based unfolding, and algorithms for constructing the unfolding. The implementation aims to develop tools for son-based model visualisation, simulation and analysis. An open source tool called SONCraft has been developed to support these functionalities. SONCraft provides a user-friendly graphical interface that facilitates model entry, supports interactive visual simulation, and allows the use of a set of analytical tools for model checking.supported in part by EPSRC EP/K001698/1 UNderstanding COmplex system eVolution through structurEd behaviouRs (UNCOVER) project

Timed unfoldings for networks of timed automata

Abstract. Whereas partial order methods have proved their efficiency for the analysis of discrete-event systems, their application to timed systems remains a challenging research topic. Here, we design a verification algorithm for networks of timed automata with invariants. Based on the unfolding technique, our method produces a branching process as an acyclic Petri net extended with read arcs. These arcs verify conditions on tokens without consuming them, thus expressing concurrency between conditions checks. They are useful for avoiding the explosion of the size of the unfolding due to clocks which are compared with constants but not reset. Furthermore, we attach zones to events, in addition to markings. We then compute a complete finite prefix of the unfolding. The presence of invariants goes against the concurrency since it entails a global synchronization on time. The use of read arcs and the analysis of the clock constraints appearing in invariants helps increasing the concurrency relation between events. Finally, the finite prefix can be used to decide reachability properties, and transition enabling.