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1

Circular Causality in Event Structures

Bartoletti M., Cimoli T., Pinna G. M., Zunino R.

Fundamenta Informaticae

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2014

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Vol. 134, nr 3/4

219--259

EN

We propose a model of events with circular causality, in the form of a conservative extension of Winskel’s event structures. We study the relations between this new kind of event structures and Propositional Contract Logic. Provable atoms in the logic correspond to reachable events in our event structures. Furthermore, we show a correspondence between the configurations of this new brand of event structures and the proofs in a fragment of Propositional Contract Logic.

2

Time in State Machines

Graf S., Prinz A.

Fundamenta Informaticae

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2007

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Vol. 77, nr 1,2

143-174

EN

State machines are a very general means to express computations in an implementation-independent way. There are ways to extend the abstract state machine (ASM) framework with distribution aspects, but there is no unifying framework for handling time so far. We propose event structures extended with time as a natural framework for representing state machines and their true concurrency model at a semantic level and for discussing associated time models. Constraints on these timed event structures and their traces (runs) are then used for characterising different frameworks for timed computations. This characterisation of timed frameworks is independent of ASM and allows to compare time models of different modelling formalisms. Finally, we propose some specific extensions of ASM for the expressions of time constraints in accordance with the event-based semantic framework and show the applicability of the obtained framework on an example with a standard time model and a set of consistency properties for timed computations.

3

Event Structures with Disabling/Enabling Relation and Event Automata

Pinna G.M.

Fundamenta Informaticae

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2006

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Vol. 73, nr 3

409-430

EN

In recent years the consideration that events in evolutions of concurrent systems can happen with different histories has received ground. In particular the possibility that part of the history can be abstracted away or identified, like in the collective tokens philosophy for Petri Nets, has gained the stage. The various brands of event structures considered in literature are tailored to a fixed interpretation with respect to the history of an event. We investigate the adequateness of event structures with a disabling/enabling relation, to settle a common ground for the history dependent and history independent interpretations, and we establish a relationship between event automata and these notions of event structures.

4

Event Structures for Arbitrary Disruption

Fecher H., Majster-Cederbaum M.

Fundamenta Informaticae

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2005

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Vol. 68, nr 1/2

103--130

EN

In process algebras that allow for some form of disruption, it is important to state when a process terminates. One option is to include a termination action Ö. Another approach is that the `final' executed action of a process terminates the process. The semantics of the former approach has been investigated in the literature in detail, e.g. by providing consistent true-concurrency and operational descriptions. The `final' executed action termination approach, which is more adequate for modelling, still lacks the existence of a detailed true concurrent description. In order to give a true concurrency model of such a termination view, we introduce a new class of event structures. This type of event structures models disabling by indicating sets of precursor events. We show that the introduced class of event structures has more expressive power with respect to event traces than the common event structures. We also give a classification of the expressive power in terms of sets of event traces. A consistency result of an operational and a denotational semantics is shown.

5

CR-structures

Schmitt V.

Fundamenta Informaticae

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1998

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Vol. 33, nr 1

71-83

EN

In this paper CR-structures are introduced. They consist of a slight generalization of general event structures, and supply a representation theorem for concurrency domains , - which are called here CR-domains for short. We recall that the latter domains are exactly the unfoldings of concurrent automata. This results also generalizes Droste's characterization of domains of configurations of general event structures.