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January 2023

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Paper published in Information & Computation
by Uli Fahrenberg 05 Mar '23

05 Mar '23

The following paper has been published in Information & Computation: Posets With Interfaces as a Model for Concurrency Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański We introduce posets with interfaces (iposets) and generalise their standard serial composition to a new gluing composition. In the partial order semantics of concurrency, interfaces and gluing allow modelling events that extend in time and across components. Alternativelytaking a decompositional view, interfaces allow cutting through events, while serial composition may only cut through edges of a poset. We show that iposets under gluing composition form a category, which generalises the monoid of posets under serial composition up to isomorphism. They form a 2-category when a subsumption order and a lax tensor in the form of a non-commutative parallel composition are added, which generalises the interchange monoids used for modelling series-parallel posets. We also study the gluing-parallel hierarchy of iposets, which generalises the standard series-parallel one. The class of gluing-parallel iposets contains that of series-parallel posets and the class of interval orders, which are well studied in concurrency theory, too. We also show that it is strictly contained in the class of all iposets by identifying several forbidden substructures. https://www.lrde.epita.fr/wiki/Publications/fahrenberg.22.iandc

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Paper accepted at FM 2023: Energy Problems in Finite and Timed Automata with Büchi Conditions
by Uli Fahrenberg 05 Mar '23

05 Mar '23

We are happy to announce that the following article has been accepted at the he 25th International Symposium on Formal Methods (FM 2023) to be held in Lübeck in March 2023: Energy Problems in Finite and Timed Automata with Büchi Conditions Sven Dziadek, Uli Fahrenberg and Philipp Schlehuber-Caissier Abstract: We show how to efficiently solve energy Büchi problems in finite weighted Büchi automata and in one-clock weighted timed Büchi automata; all our algorithms are implemented in a pipeline based on TChecker and Spot. Solving the latter problem is done by using the corner-point abstraction; the former problem is handled by a modified version of Bellman-Ford interleaved with Couvreur's algorithm. The paper is available at https://arxiv.org/abs/2205.04392

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