Characterising Probabilistic Processes Logically

In this paper we work on (bi)simulation semantics of processes that exhibit both nondeterministic and probabilistic behaviour. We propose a probabilistic extension of the modal mu-calculus and show how to derive characteristic formulae for various simulation-like preorders over finite-state processes without divergence. In addition, we show that even without the fixpoint operators this probabilistic mu-calculus can be used to characterise these behavioural relations in the sense that two states are equivalent if and only if they satisfy the same set of formulae.Comment: 18 page

Multiset Bisimulations as a Common Framework for Ordinary and Probabilistic Bisimulations

Our concrete objective is to present both ordinary bisimulations and probabilistic bisimulations in a common coalgebraic framework based on multiset bisimulations. For that we show how to relate the underlying powerset and probabilistic distributions functors with the multiset functor by means of adequate natural transformations. This leads us to the general topic that we investigate in the paper: a natural transformation from a functor F to another G transforms F-bisimulations into G-bisimulations but, in general, it is not possible to express G-bisimulations in terms of F-bisimulations. However, they can be characterized by considering Hughes and Jacobs’ notion of simulation, taking as the order on the functor F the equivalence induced by the epi-mono decomposition of the natural transformation relating F and G. We also consider the case of alternating probabilistic systems where non-deterministic and probabilistic choices are mixed, although only in a partial way, and extend all these results to categorical simulations

QRB-DOMAINS AND THE PROBABILISTIC POWERDOMAIN ∗

Vol. 8 (1:14) 2012, pp. 1–3

Unifying Probability with Nondeterminism

Early support for reasoning about probabilistic system behaviour replaced nondeterminism with probabilism. Only relatively recently have formalisms been studied that combine the two, and hence facilitate reasoning about. probabilistic systems at levels of abstraction more general than code. Such studies have revealed an unsuspected subtlety in the interaction between nondeterministic mid probabilistic choices that; can be summarised: the demon resolving the nondeterministic choice has memory of previous state changes, whilst the probabilistic choice is made spontaneously. As a. result, assignments to distinct variables need no longer commute. This paper introduces a model with explicit control of the length of the demon's memory. It, does so by expanding the standard (initial-final) state view of computation to incorporate a third state, the 'original' state which checkpoints the most recent nondeterministic choice. That enables a nondeterministic choice to he made on the basis of only certain past probabilistic choices and so facilitates independent nondeterministic combinations to be chosen against just, those. Sound laws are presented and used to analyse first an example in which no new behaviour should result, and second one that lies beyond the scope of traditional models.Computer Science, Software EngineeringComputer Science, Theory & MethodsEICPCI-S(ISTP)

Weiterentwickelte Modellansaetze chemischer und physikalischer Effekte im Grubengebaeude eines Endlagers im Salinar

The study examines the radioactivity transport within an underground mine structure by means of a simplified structural model. This approach yields relative results on the significance of sorption processes, but will not deliver absolute results for safety assessments. The containment of nuclides within the close-in area is simulated by a linear approach describing sorption according to the K_d-concept, with the K_d values being varied for determination of the effects of sorption. The report firstly explains the underground mine structure considered and the modelling assumptions and effects of the release and transport calculations, as well as, in great detail, the modelling of sorption processes in the underground structure. Then the modelling computations performed and the movement of brines are discussed, brines being salt solutions entering the underground structure from the outside of the mine or flowing in from the host rock. Further aspects examined are the effects of sorption processes along a snicket gate within the structure, or within the emplacement area. The two variants are comparatively analysed, and the concluding chapter shows the effects of sorption by a model combining the two variants. (orig./DG)In der Studie wird der Aktivitaetstransport im Grubengebaeude anhand einer vereinfachten Grubengebaeudestruktur untersucht. Hierdurch sind relative Aussagen zur Bedeutung der Sorption, jedoch keine Absolutaussagen zur Bewertung der Sicherheit des Endlagers moeglich. Die Rueckhaltung der Nuklide im Nahbereich wird mit einem linearen Sorptionsansatz nach dem K_d-Konzept realisiert, wobei die K_d-Werte zur Feststellung des Einflusses der Sorption variiert werden. Zunaechst werden die betrachtete Grubengebaeudestruktur und die Modellannahmen und Effekte der Freisetzungs- und Ausbreitungsrechnungen sowie im Detail die Modellierung der Sorption im Grubengebaeude erlaeutert. Danach wird auf die durchgefuehrten Modellrechnungen und auf die Laugenbewegung eingegangen. Mit Lauge wird die von aussen oder aus dem Wirtsgestein in das Grubengebaeude zugeflossene Salzloesung bezeichnet. Weiterhin werden die Auswirkungen der Sorption innerhalb einer Verbindungsstrecke im Grubengebaeude und die Sorption innerhalb des Einlagerungsbereichs behandelt sowie die beiden Varianten verglichen und abschliessend erfolgt die Darstellung des Sorptionseinflusses fuer die Kombination beider Varianten. (orig./DG)SIGLEAvailable from TIB Hannover: RN 6050(123) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman