74 research outputs found
Transition system specifications with negative premises
AbstractIn this article the general approach to Plotkin-style operational semantics of Groote and Vaandrager (1989) is extended to transition system specifications (TSSs) with rules that may contain negative premises. Two problems arise: firstly the rules may be inconsistent, and secondly it is not obvious how a TSS determines a transition relation. We present a general method, based on the stratification technique in logic programming, to prove consistency of a set of rules and we show how a specific transition relation can be associated with a TSS in a natural way. Then a special format for the rules, the ntyft/ntyxt format, is defined. It is shown that for this format three important theorems hold. The first theorem says that bisimulation is a congruence if all operators are defined using this format. The second theorem states that, under certain restrictions, a TSS in ntyft format can be added conservatively to a TSS in pure ntyft/ntyxt format. Finally, it is shown that the trace congruence for image-finite processes induced by the pure ntyft/ntyxt format is precisely bisimulation equivalence
Operational Semantics of Process Monitors
CSPe is a specification language for runtime monitors that can directly
express concurrency in a bottom-up manner that composes the system from
simpler, interacting components. It includes constructs to explicitly flag
failures to the monitor, which unlike deadlocks and livelocks in conventional
process algebras, propagate globally and aborts the whole system's execution.
Although CSPe has a trace semantics along with an implementation demonstrating
acceptable performance, it lacks an operational semantics. An operational
semantics is not only more accessible than trace semantics but also
indispensable for ensuring the correctness of the implementation. Furthermore,
a process algebra like CSPe admits multiple denotational semantics appropriate
for different purposes, and an operational semantics is the basis for
justifying such semantics' integrity and relevance. In this paper, we develop
an SOS-style operational semantics for CSPe, which properly accounts for
explicit failures and will serve as a basis for further study of its
properties, its optimization, and its use in runtime verification
Lean and Full Congruence Formats for Recursion
In this paper I distinguish two (pre)congruence requirements for semantic
equivalences and preorders on processes given as closed terms in a system
description language with a recursion construct. A lean congruence preserves
equivalence when replacing closed subexpressions of a process by equivalent
alternatives. A full congruence moreover allows replacement within a recursive
specification of subexpressions that may contain recursion variables bound
outside of these subexpressions.
I establish that bisimilarity is a lean (pre)congruence for recursion for all
languages with a structural operational semantics in the ntyft/ntyxt format.
Additionally, it is a full congruence for the tyft/tyxt format.Comment: To appear in: Proc. LICS'17, Reykjavik, Iceland, IEE
Causality in the Semantics of Esterel: Revisited
We re-examine the challenges concerning causality in the semantics of Esterel
and show that they pertain to the known issues in the semantics of Structured
Operational Semantics with negative premises. We show that the solutions
offered for the semantics of SOS also provide answers to the semantic
challenges of Esterel and that they satisfy the intuitive requirements set by
the language designers
Pushdown Automata and Context-Free Grammars in Bisimulation Semantics
The Turing machine models an old-fashioned computer, that does not interact with the user or with other computers, and only does batch processing. Therefore, we came up with a Reactive Turing Machine that does not have these shortcomings. In the Reactive Turing Machine, transitions have labels to give a notion of interactivity. In the resulting process graph, we use bisimilarity instead of language equivalence.
Subsequently, we considered other classical theorems and notions from automata theory and formal languages theory. In this paper, we consider the classical theorem of the correspondence between pushdown automata and context-free grammars. By changing the process operator of sequential composition to a sequencing operator with intermediate acceptance, we get a better correspondence in our setting. We find that the missing ingredient to recover the full correspondence is the addition of a notion of state awareness
Parallel Pushdown Automata and Commutative Context-Free Grammars in Bisimulation Semantics (Extended Abstract)
A classical theorem states that the set of languages given by a pushdown
automaton coincides with the set of languages given by a context-free grammar.
In previous work, we proved the pendant of this theorem in a setting with
interaction: the set of processes given by a pushdown automaton coincides with
the set of processes given by a finite guarded recursive specification over a
process algebra with actions, choice, sequencing and guarded recursion, if and
only if we add sequential value passing. In this paper, we look what happens if
we consider parallel pushdown automata instead of pushdown automata, and a
process algebra with parallelism instead of sequencing.Comment: In Proceedings EXPRESS/SOS2023, arXiv:2309.05788. arXiv admin note:
text overlap with arXiv:2203.0171
Rooted branching bisimulation as a congruence for probabilistic transition systems
Ponencia presentada en el 13 International Workshop on Quantitative Aspects of Programming Languages and Systems. London, United Kingdom, April 11-12, 2015.We propose a probabilistic transition system specification format, referred to as probabilistic RBB safe, for which rooted branching bisimulation is a congruence. The congruence theorem is based on the approach of Fokkink for the qualitative case. For this to work, the theory of transition system specifications in the setting of labeled transition systems needs to be extended to deal with probability distributions, both syntactically and semantically. We provide a scheduler-free characterization of probabilistic branching bisimulation as adapted from work of Andova et al. for the alternating model. Counter examples are given to justify the various conditions required by the format.Fil: Lee, Matías David. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: De Vink, Erik P. Eindhoven University of Technology; The Netherlands.Fil: De Vink, Erik P. Centrum Wiskunde & Informatica; The Netherlands.Ciencias de la Computació
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