Tree rules in probabilistic transition system specifications with negative and quantitative premises

Probabilistic transition system specifications (PTSSs) in the ntmufnu/ntmuxnu format provide structural operational semantics for Segala-type systems that exhibit both probabilistic and nondeterministic behavior and guarantee that isimilarity is a congruence.Similar to the nondeterministic case of rule format tyft/tyxt, we show that the well-foundedness requirement is unnecessary in the probabilistic setting. To achieve this, we first define an extended version of the ntmufnu/ntmuxnu format in which quantitative premises and conclusions include nested convex combinations of distributions. This format also guarantees that bisimilarity is a congruence. Then, for a given (possibly non-well-founded) PTSS in the new format, we construct an equivalent well-founded transition system consisting of only rules of the simpler (well-founded) probabilistic ntree format. Furthermore, we develop a proof-theoretic notion for these PTSSs that coincides with the existing stratification-based meaning in case the PTSS is stratifiable. This continues the line of research lifting structural operational semantic results from the nondeterministic setting to systems with both probabilistic and nondeterministic behavior.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244

Equivalence checking for weak bi-kleene algebra∗

Pomset automata are an operational model of weak bi-Kleene algebra, which describes programs that can fork an execution into parallel threads, upon completion of which execution can join to resume as a single thread. We characterize a fragment of pomset automata that admits a decision procedure for language equivalence. Furthermore, we prove that this fragment corresponds precisely to series-rational expressions, i.e., rational expressions with an additional operator for bounded parallelism. As a consequence, we obtain a new proof that equivalence of series-rational expressions is decidable

Brzozowski goes concurrent - A kleene theorem for pomset languages

Concurrent Kleene Algebra (CKA) is a mathematical formalism to study programs that exhibit concurrent behaviour. As with previous extensions of Kleene Algebra, characterizing the free model is crucial in order to develop the foundations of the theory and potential applications. For CKA, this has been an open question for a few years and this paper makes an important step towards an answer. We present a new automaton model and a Kleene-like theorem that relates a relaxed version of CKA to series-parallel pomset languages, which are a natural candidate for the free model. There are two substantial differences with previous work: from expressions to automata, we use Brzozowski derivatives, which enable a direct construction of the automaton; from automata to expressions, we provide a syntactic characterization of the automata that denote valid CKA behaviours

Equivalence checking for weak bi-Kleene algebra

Pomset automata are an operational model of weak bi-Kleene algebra, which describes programs that can fork an execution into parallel threads, upon completion of which execution can join to resume as a single thread. We characterize a fragment of pomset automata that admits a decision procedure for language equivalence. Furthermore, we prove that this fragment corresponds precisely to series-rational expressions, i.e., rational expressions with an additional operator for bounded parallelism. As a consequence, we obtain a new proof that equivalence of series-rational expressions is decidable

WoesteLand : effecten en motieven bij vijftig jaar natuurbeschermingskampen voor jongeren

WoesteLand is de landelijke jongerenwerkgroep van het IVN, Instituut voor natuureducatie en duurzaamheid. De werkgroep organiseert al vijftig jaar activiteiten in de natuur voor en door jongeren van 12 tot 30 jaar. Tijdens de kampen wordt vrijwilligerswerk in de natuur gedaan. Het enthousiasme van de deelnemers weerlegt de stelling dat jongeren van 12 tot 30 jaar in het algemeen geen belangstelling hebben voor natuur. WoesteLand biedt naast de natuurervaring ook een sociale ervaring, en die combinatie werkt goed bij deze doelgroep. WoesteLanders hebben en houden hart voor de natuur. Dit uit zich in opleidings- en beroepskeuze, in levensstijl en in de opvoeding die zij hun kinderen geven. Daarmee werkt het door naar de volgende generaties. Een relatief groot deel van hen wordt lid van een natuurorganisatie

A Logic with Reverse Modalities for History-preserving Bisimulations

We introduce event identifier logic (EIL) which extends Hennessy-Milner logic by the addition of (1) reverse as well as forward modalities, and (2) identifiers to keep track of events. We show that this logic corresponds to hereditary history-preserving (HH) bisimulation equivalence within a particular true-concurrency model, namely stable configuration structures. We furthermore show how natural sublogics of EIL correspond to coarser equivalences. In particular we provide logical characterisations of weak history-preserving (WH) and history-preserving (H) bisimulation. Logics corresponding to HH and H bisimulation have been given previously, but not to WH bisimulation (when autoconcurrency is allowed), as far as we are aware. We also present characteristic formulas which characterise individual structures with respect to history-preserving equivalences.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407

Landbouw natuurlijk : over het meten van natuurkwaliteit in het agrarisch gebied

De studie bestaat uit vier deelprojecten: 1) Koppelingen tussen landbouw en natuur. 2) Effectiviteit agrarisch natuurbeheer. 3) Graadmeters. 4) Instrumentarium beleidsanalyse

Blue Challenge Program: een nieuwe combinatie van diensten voor een duurzame aquacultuur

Een overzicht van actuele ontwikkelingen binnen de aquacultuur en daaraan gekoppeld de mogelijkheden (kansen) om die ontwikkelingen versneld in gang te zette