517 research outputs found
Behavioural Types for Actor Systems
Recent mainstream programming languages such as Erlang or Scala have renewed
the interest on the Actor model of concurrency. However, the literature on the
static analysis of actor systems is still lacking of mature formal methods. In
this paper we present a minimal actor calculus that takes as primitive the
basic constructs of Scala's Actors API. More precisely, actors can send
asynchronous messages, process received messages according to a pattern
matching mechanism, and dynamically create new actors, whose scope can be
extruded by passing actor names as message parameters. Drawing inspiration from
the linear types and session type theories developed for process calculi, we
put forward a behavioural type system that addresses the key issues of an actor
calculus. We then study a safety property dealing with the determinism of
finite actor com- munication. More precisely, we show that well typed and
balanced actor systems are (i) deadlock-free and (ii) any message will
eventually be handled by the target actor, and dually no actor will
indefinitely wait for an expected messag
The role of concurrency in an evolutionary view of programming abstractions
In this paper we examine how concurrency has been embodied in mainstream
programming languages. In particular, we rely on the evolutionary talking
borrowed from biology to discuss major historical landmarks and crucial
concepts that shaped the development of programming languages. We examine the
general development process, occasionally deepening into some language, trying
to uncover evolutionary lineages related to specific programming traits. We
mainly focus on concurrency, discussing the different abstraction levels
involved in present-day concurrent programming and emphasizing the fact that
they correspond to different levels of explanation. We then comment on the role
of theoretical research on the quest for suitable programming abstractions,
recalling the importance of changing the working framework and the way of
looking every so often. This paper is not meant to be a survey of modern
mainstream programming languages: it would be very incomplete in that sense. It
aims instead at pointing out a number of remarks and connect them under an
evolutionary perspective, in order to grasp a unifying, but not simplistic,
view of the programming languages development process
Actors vs Shared Memory: two models at work on Big Data application frameworks
This work aims at analyzing how two different concurrency models, namely the
shared memory model and the actor model, can influence the development of
applications that manage huge masses of data, distinctive of Big Data
applications. The paper compares the two models by analyzing a couple of
concrete projects based on the MapReduce and Bulk Synchronous Parallel
algorithmic schemes. Both projects are doubly implemented on two concrete
platforms: Akka Cluster and Managed X10. The result is both a conceptual
comparison of models in the Big Data Analytics scenario, and an experimental
analysis based on concrete executions on a cluster platform
Logical Characterizations of Behavioral Relations on Transition Systems of Probability Distributions
Probabilistic nondeterministic processes are commonly modeled as probabilistic LTSs (PLTSs). A number of logical characterizations of the main behavioral relations on PLTSs have been studied. In particular, Parma and Segala [2007] and Hermanns et al. [2011] define a probabilistic Hennessy-Milner logic interpreted over probability distributions, whose corresponding logical equivalence/preorder when restricted to Dirac distributions coincide with standard bisimulation/simulation between the states of a PLTS. This result is here extended by studying the full logical equivalence/preorder between (possibly non-Dirac) distributions in terms of a notion of bisimulation/simulation defined on a LTS whose states are distributions (dLTS). We show that the well-known spectrum of behavioral relations on nonprobabilistic LTSs as well as their corresponding logical characterizations in terms of Hennessy-Milner logic scales to the probabilistic setting when considering dLTSs
A Logic for True Concurrency
We propose a logic for true concurrency whose formulae predicate about events
in computations and their causal dependencies. The induced logical equivalence
is hereditary history preserving bisimilarity, and fragments of the logic can
be identified which correspond to other true concurrent behavioural
equivalences in the literature: step, pomset and history preserving
bisimilarity. Standard Hennessy-Milner logic, and thus (interleaving)
bisimilarity, is also recovered as a fragment. We also propose an extension of
the logic with fixpoint operators, thus allowing to describe causal and
concurrency properties of infinite computations. We believe that this work
contributes to a rational presentation of the true concurrent spectrum and to a
deeper understanding of the relations between the involved behavioural
equivalences.Comment: 31 pages, a preliminary version appeared in CONCUR 201
Causality in concurrent systems
Concurrent systems identify systems, either software, hardware or even
biological systems, that are characterized by sets of independent actions that
can be executed in any order or simultaneously. Computer scientists resort to a
causal terminology to describe and analyse the relations between the actions in
these systems. However, a thorough discussion about the meaning of causality in
such a context has not been developed yet. This paper aims to fill the gap.
First, the paper analyses the notion of causation in concurrent systems and
attempts to build bridges with the existing philosophical literature,
highlighting similarities and divergences between them. Second, the paper
analyses the use of counterfactual reasoning in ex-post analysis in concurrent
systems (i.e. execution trace analysis).Comment: This is an interdisciplinary paper. It addresses a class of causal
models developed in computer science from an epistemic perspective, namely in
terms of philosophy of causalit
Secrecy in Untrusted Networks
We investigate the protection of migrating agents against the untrusted sites they traverse. The resulting calculus provides a formal framework to reason about protection policies and security protocols over distributed, mobile infrastructures, and aims to stand to ambients as the spi calculus stands to ?. We present a type system that separates trusted and untrusted data and code, while allowing safe interactions with untrusted sites. We prove that the type system enforces a privacy property, and show the expressiveness of the calculus via examples and an encoding of the spi calculus
Beyond black and white: the Italian reception of the debate on Native Indian commentaries in nineteenth-century Vedic studies
This article discusses the nineteenth-century debate between German and British Indologists on ancient Indian commentators, shedding light on how Italian Indol- ogists received and responded to this discussion. It reveals why Italian scholars, although trained under the most eminent German philologists, often disagreed on the status of native commentaries, sometimes viewing them as an unreliable guide to interpreting the Vedas and other texts. Moreover, Italian criticisms of the German approach to ancient Indian texts reflected differences in the ideological concerns underpinning the hegemonic discourses between Europe and India. Because of both transnational reception and nation-building concerns, the history of Italian Indological studies represents a unique perspective in the context of European approaches to the subcontinent
Migration and Autism Diagnosis
Clinicians in many countries are increasingly working with children from migrant families. Although autism is diagnosed at an approximately equal rate in children in developed countries internationally (estimated 1% of the population), many studies report that children in migrant communities are at relatively higher risk for autism. Risk factors as well as symptom rates appear to vary across cultures. This chapter reviews the current state of the science and outlines conceptual considerations for clinicians assessing foreign, migrant, and minority children for diagnosis of autism. Possible reasons for higher rates among migrant children are discussed and suggestions for clinical evaluation are made
Name-passing calculi and crypto-primitives: A survey
The paper surveys the literature on high-level name-passing process calculi, and their extensions with cryptographic primitives. The survey is by no means exhaustive, for essentially two reasons. First, in trying to provide a coherent presentation of different ideas and techniques, one inevitably ends up leaving out the approaches that do not fit the intended roadmap. Secondly, the literature on the subject has been growing at very high rate over the years. As a consequence, we decided to concentrate on few papers that introduce the main ideas, in the hope that discussing them in some detail will provide sufficient insight for further reading
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