59 research outputs found
Semantic subtyping for objects and classes
In this paper we propose an integration of structural subtyping with boolean
connectives and semantic subtyping to define a Java-like programming language
that exploits the benefits of both techniques. Semantic subtyping is an approach
for defining subtyping relation based on set-theoretic models, rather than syntactic
rules. On the one hand, this approach involves some non trivial mathematical
machinery in the background. On the other hand, final users of the language need
not know this machinery and the resulting subtyping relation is very powerful and
intuitive. While semantic subtyping is naturally linked to the structural one, we
show how our framework can also accommodate the nominal subtyping. Several
examples show the expressivity and the practical advantages of our proposal
The Powerdomain of Indexed Valuations
This paper is about combining nondeterminism and probabilities. We study this phenomenon from a domain theoretic point of view. In domain theory, nondeterminism is modeled using the notion of powerdomain, while probability is modeled using the powerdomain of valuations. Those two functors do not combine well, as they are. We define the notion of powerdomain of indexed valuations, which can be combined nicely with the usual nondeterministic powerdomain. We show an equational characterization of our construction. Finally we discuss the computational meaning of indexed valuations, and we show how they can be used, by giving a denotational semantics of a simple imperative language
Processes, Systems \& Tests: Defining Contextual Equivalences
In this position paper, we would like to offer and defend a new template to
study equivalences between programs -- in the particular framework of process
algebras for concurrent computation.We believe that our layered model of
development will clarify the distinction that is too often left implicit
between the tasks and duties of the programmer and of the tester. It will also
enlighten pre-existing issues that have been running across process algebras as
diverse as the calculus of communicating systems, the -calculus -- also
in its distributed version -- or mobile ambients.Our distinction starts by
subdividing the notion of process itself in three conceptually separated
entities, that we call \emph{Processes}, \emph{Systems} and \emph{Tests}.While
the role of what can be observed and the subtleties in the definitions of
congruences have been intensively studied, the fact that \emph{not every
process can be tested}, and that \emph{the tester should have access to a
different set of tools than the programmer} is curiously left out, or at least
not often formally discussed.We argue that this blind spot comes from the
under-specification of contexts -- environments in which comparisons takes
place -- that play multiple distinct roles but supposedly always \enquote{stay
the same}.We illustrate our statement with a simple Java example, the
\enquote{usual} concurrent languages, but also back it up with
-calculus and existing implementations of concurrent languages as
well
A compositional semantics for the reversible pi-calculus
International audienceWe introduce a labelled transition semantics for the reversible pi-calculus. It is the first account of a com- positional definition of a reversible calculus, that has both concurrency primitives and name mobility. The notion of reversibility is strictly linked to the notion of causality. We discuss the notion of causality induced by our calculus, and we compare it with the existing notions in the literature, in particular for what concerns the syntactic feature of scope extrusion, typical of the pi-calculus
Probabilistic event structures and domains
AbstractThis paper studies how to adjoin probability to event structures, leading to the model of probabilistic event structures. In their simplest form, probabilistic choice is localised to cells, where conflict arises; in which case probabilistic independence coincides with causal independence. An event structure is associated with a domain—that of its configurations ordered by inclusion. In domain theory, probabilistic processes are denoted by continuous valuations on a domain. A key result of this paper is a representation theorem showing how continuous valuations on the domain of a confusion-free event structure correspond to the probabilistic event structures it supports. We explore how to extend probability to event structures which are not confusion-free via two notions of probabilistic runs of a general event structure. Finally, we show how probabilistic correlation and probabilistic event structures with confusion can arise from event structures which are originally confusion-free by using morphisms to rename and hide events
for Probabilistic Computation
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The powerdomain of indexed valuations
Reproduction of all or part of this work is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent BRICS Report Series publications. Copies may be obtained by contacting: BRIC
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