On the Unification of Process Semantics: Observational Semantics (original) (raw)
Related papers
On the Unification of Process Semantics: Equational Semantics
Electronic Notes in Theoretical Computer Science, 2009
The complexity of parallel systems has produced a large collection of semantics for processes, a classification of which is provided by Van Glabbeek's linear time-branching time spectrum; however, no suitable unified definitions were available. We have discovered the way to unify them, both in an observational framework and by means of a quite small set of parameterized (in)equations that provide a sound and complete axiomatization of the preorders that define them. In more detail, we have proved that we only need a generic simulation axiom (NS), which defines the family of constrained simulation semantics, thus covering the class of branching time semantics, and a generic axiom (ND) for reducing the non-determinism of processes, by means of which we introduce the additional identifications induced by each of the linear time semantics.
Unifying the Linear Time-Branching Time Spectrum of Process Semantics
Logical Methods in Computer Science, 2013
Van Glabbeek's linear time-branching time spectrum is one of the most relevant work on comparative study on process semantics, in which semantics are partially ordered by their discrimination power. In this paper we bring forward a refinement of this classification and show how the process semantics can be dealt with in a uniform way: based on the very natural concept of constrained simulation we show how we can classify the spectrum in layers; for the families lying in the same layer we show how to obtain in a generic way equational, observational, logical and operational characterizations; relations among layers are also very natural and differences just stem from the constraint imposed on the simulations that rule the layers. Our methodology also shows how to achieve a uniform treatment of semantic preorders and equivalences.
2013
The complexity of parallel systems has produced a large collection of semantics for processes. Van Glabbeek's linear time-branching time spectrum provides a classification of most of these semantics; however, no suitable unified definitions were available. We have discovered how to unify them, both in an observational framework and in an equational framework. In this first part of our study we present the observational semantics, that stresses the differences between the simulation (branching) semantics and the extentional (linear) semantics. As a result we rediscover the classification in van Glabbeek's spectrum and shed light on it, obtaining a framework where we can consider all the semantics in the spectrum at the same time. Also, we have discovered some "lost links" that correspond to semantics, possibly not too interesting (at the moment), that provide a clearer picture of the spectrum.
(Bi)simulations up-to characterise process semantics
Information and Computation, 2009
Bisimulations up-to Simulations up-to Canonical preorder Linear time-branching time spectrum We define (bi)simulations up-to a preorder and show how we can use them to provide a coinductive, (bi)simulation-like, characterisation of semantic (equivalences) preorders for processes. In particular, we can apply our results to all the semantics in the linear timebranching time spectrum that are defined by preorders coarser than the ready simulation preorder. The relation between bisimulations up-to and simulations up-to allows us to find some new relations between the equivalences that define the semantics and the corresponding preorders. In particular, we have shown that the simulation up-to an equivalence relation is a canonical preorder whose kernel is the given equivalence relation. Since all of these canonical preorders are defined in an homogeneous way, we can prove properties for them in a generic way. As an illustrative example of this technique, we generate an axiomatic characterisation of each of these canonical preorders, that is obtained simply by adding a single axiom to the axiomatization of the original equivalence relation. Thus we provide an alternative axiomatization for any axiomatizable preorder in the linear time-branching time spectrum, whose correctness and completeness can be proved once and for all. Although we first prove, by induction, our results for finite processes, then we see, by using continuity arguments, that they are also valid for infinite (finitary) processes.
On the Unification of Process Semantics: Logical Semantics
Electronic Proceedings in Theoretical Computer Science, 2011
We continue with the task of obtaining a unifying view of process semantics by considering in this case the logical characterization of the semantics. We start by considering the classic linear timebranching time spectrum developed by R.J. van Glabbeek. He provided a logical characterization of most of the semantics in his spectrum but, without following a unique pattern. In this paper, we present a uniform logical characterization of all the semantics in the enlarged spectrum. The common structure of the formulas that constitute all the corresponding logics gives us a much clearer picture of the spectrum, clarifying the relations between the different semantics, and allows us to develop generic proofs of some general properties of the semantics.
Universal Coinductive Characterisations of Process Semantics
IFIP International Federation for Information Processing, 2008
We present a theoretical framework which allows to define in a uniform way coinductive characterisations of nearly any semantic preorder or equivalence between processes, by means of simulations up-to and bisimulations up-to. In particular, all the semantics in the linear time-branching time spectrum are covered. Constrained simulations, that generalise plain simulations by including a constraint that all the pairs of related processes must satisfy, are the key to obtain such a general framework. We provide a simple axiomatisation of any constrained simulation preorder and also for the corresponding equivalence. These axiomatizations allow us to prove in a uniform way that each constrained simulation preorder (equivalence) defines a class of process preorders (equivalences) which share commons properties, like the possibility of giving coinductive characterisations for all of them, or the existence of a canonical preorder inducing each of these equivalences.
Denotational Semantics for Process-Based Simulation Languages. Part II
1998
In this paper we present a method for translating the synchronisation behaviour of a process oriented discrete event simulation language into a process algebra. Such translations serve two purposes. The rst exploits the formal structure of the target process algebraic representations to provide proofs of properties of the source system (such as deadlock freedom, fairness, liveness, ...) which can be very di cult to establish by simulation experiment. The second exploits the denotational semantics to better understand the language constructs as abstract entities and to reason about simulation models. Here we give the intuition and present the basic mechanisms using the Demos simulation language and the CCS and SCCS process algebras. The analysis of the synchronisations of full Demos is treated in a companion paper.
A denotational semantics for a process-based simulation language
Acm Transactions on Modeling and Computer Simulation, 1998
In this paper we present a method for translating the synchronisation behaviour of a process oriented discrete event simulation language into a process algebra. Such translations serve two purposes. The rst exploits the formal structure of the target process algebraic representations to provide proofs of properties of the source system (such as deadlock freedom, fairness, liveness, ...) which can be very di cult to establish by simulation experiment. The second exploits the denotational semantics to better understand the language constructs as abstract entities and to reason about simulation models. Here we give the intuition and present the basic mechanisms using the Demos simulation language and the CCS and SCCS process algebras. The analysis of the synchronisations of full Demos is treated in a companion paper.
Designing equivalent semantic models for process creation
Theoretical Computer Science, 1988
Operational and denotational semantic models are designed for languages with process creation, and the relationships between the two semantics are investigated, The presentation is organized in four sections dealing with a uniform and static, a uniform and dynamic, a nonuniform and static, and a nonuniform and dynamic language respectively. Here uniform/nonuniform refers to a language with uninterpreted/interpreted elementary actions, and static/dynamic to the distinction between languages with a fixed/growing number of parallel processes. The contrast between uniform and nonuniform is reflected in the use of linear time versus branching time models, the latter employing a version of Plotkin's resumptions. The operational semantics make use of Hennessy's and Plotkin's transition systems. All models are built on metric structures, and involve continuations in an essential way. The languages studied are abstractions of the parallel object-oriented language POOL for which we have designed separate operational and denotational semantics in earlier work. The pappr provides a full analysis of the relationship between the two semantics for these abstractions. Technically, a key role is played by a new operator which is able to decide dynamically whether it should act as sequential or parallel composition. 110 114 114 II4 I18 121 121 123 125 129 132 * Most of this work has been carried out in the context of ESPRIT Project 415: Parallel Architectures and Languages for Adtnmced Information Rwwsing: A VLSI-directed Approach. 0304.3975/88/$3.50 @ 1988, Elsevier Science Publishers B.V. (North-Holland) i? America, J. De Bakker 4.