A Forward Reachability Algorithm for Bounded Timed-Arc Petri Nets

Timed-arc Petri nets (TAPN) are a well-known time extension of the Petri net model and several translations to networks of timed automata have been proposed for this model. We present a direct, DBM-based algorithm for forward reachability analysis of bounded TAPNs extended with transport arcs, inhibitor arcs and age invariants. We also give a complete proof of its correctness, including reduction techniques based on symmetries and extrapolation. Finally, we augment the algorithm with a novel state-space reduction technique introducing a monotonic ordering on markings and prove its soundness even in the presence of monotonicity-breaking features like age invariants and inhibitor arcs. We implement the algorithm within the model-checker TAPAAL and the experimental results document an encouraging performance compared to verification approaches that translate TAPN models to UPPAAL timed automata.Comment: In Proceedings SSV 2012, arXiv:1211.587

Undecidability of Coverability and Boundedness for Timed-Arc Petri Nets with Invariants

Timed-Arc Petri Nets (TAPN) is a well studied extension of the classical Petri net model where tokens are decorated with real numbers that represent their age. Unlike reachability, which is known to be undecidable for TAPN, boundedness and coverability remain decidable. The model is supported by a recent tool called TAPAAL which, among others, further extends TAPN with invariants on places in order to model urgency. The decidability of boundedness and coverability for this extended model has not yet been considered. We present a reduction from two-counter Minsky machines to TAPN with invariants to show that both the boundedness and coverability problems are undecidable

Viborg Kommune styrer efter en sammenhængsmodel

I 2017 havde Viborg Kommune en styringsmodel med mere end 50 politikker og strategier indeholdende et væld af målsætninger. Det var ikke tydeligt, hvad der var byrådets højest prioriterede målsætninger, og der var ikke en synlig, overordnet retning for udviklingen af Viborg Kommune. De fleste målsætninger var indenfor de respektive sektorer, og der var ikke på tværs af den politiske og administrative organisation bredt ejerskab til det samlede kompleks af politikker og strategier. I denne artikel kan du læse om, hvordan Viborg Kommune er i fuld gang med en markant forandring. Målet er at skabe sammenhæng for borgeneud fra en tydelig politisk retning og prioritering af de vigtigste målsætninger