1,721,257 research outputs found
Modelling global computations with Klaim
No full textAbstract. A new area of research, known as Global Computing, is by now well established. It aims at defining new models of computation based on code and data mobility over wide-area networks with highly dynamic topologies, and at providing infrastructures to support coordination and control of components originating from different, possibly untrusted, fault-prone, malicious or selfish sources. In this paper, we present our contribution to the field of Global Computing that is centred on Kernel Language for Agents Interaction and Mobility (Klaim ). Klaim is an experimental language specifically designed to programme distributed systems consisting of several mobile components that interact through multiple distributed tuple spaces. We present some of the key notions of the language and discuss how its formal semantics can be exploited to reason about qualitative and quantitative aspects of the specified systems
A modal logic for mobile agents
No full textKlaim is an experimental programming language that supports a programming paradigm where both processes and data can be moved across different computing environments. The language relies on the use of explicit localities. This paper presents a temporal logic for specifying properties of Klaim programs. The logic is inspired by Hennessy-Milner Logic (HML) and the μ-calculus, but has novel features that permit dealing with state properties and impact of actions and movements over the different sites. The logic is equipped with a complete proof system that enables one to prove properties of mobile systems
Implementing Mobile and Distributed Applications in X-Klaim
No full textIn this paper we present X-Klaim, an experimental programming
language specifically designed to program distributed systems
composed of several components interacting through multiple
distributed tuple spaces and mobile code. The language consists of a
set of coordination primitives inspired by Linda, a set of operators
for building processes borrowed from process algebras and a few
classical constructs for sequential programming. We present some
programming examples in X-Klaim, dealing with mobile code
programming paradigms, such as client-server, code mobility and
mobile agents
Formal Methods for the Quantitative Evaluation of Collective Adaptive Systems (SFM 2016)
No full textRevisiting bisimilarity and its modal logic for nondeterministic and probabilistic processes
Full text linkThe logic PML is a probabilistic version of Hennessy–Milner logic introduced by Larsen and Skou to characterize bisimilarity over probabilistic processes without internal nondeterminism. In this paper, two alternative interpretations of PML over nondeterministic and probabilistic processes as models are considered, and two new bisimulation-based equivalences that are in full agreement with those interpretations are provided. The new equivalences include as coarsest congruences the two bisimilarities for nondeterministic and probabilistic processes proposed by Segala and Lynch. The latter equivalences are instead known to agree with two versions of Hennessy–Milner logic extended with an additional probabilistic operator interpreted over state distributions in place of individual states. The new interpretations of PML and the corresponding new bisimilarities are thus the first ones to offer a uniform framework for reasoning on processes that are purely nondeterministic or reactive probabilistic or that mix nondeterminism and probability in an alternating/nonalternating way
Initial algebra for a system of right-linear functors
Full text linkIn 2003 we showed that right-linear systems of equations over regular expressions, when interpreted in a category of trees, have a solution when ever they enjoy a specific property that we called hierarchicity and that is instrumental to avoid critical mutual recursive definitions. In this note, we prove that a right-linear system of polynomial endofunctors on a cocartesian monoidal closed category which enjoys parameterized left list arithmeticity, has an initial algebra, provided it satisfies a property similar to hierarchicity
Multiple-Labelled Transition Systems for nominal calculi and their logics
No full textAction-labelled transition systems (LTSs) have proved to be a fundamental model for describing and proving properties of concurrent systems. In this paper we introduce Multiple-Labelled Transition Systems (MLTSs) as generalisations of LTSs that enable us to deal with system features that are becoming increasingly important when considering languages and models for network-aware programming. MLTSs enable us to describe not only the actions that systems can perform but also their usage of resources and their handling (creation, revelation . . .) of names; these are essential for modelling changing evaluation environments. We also introduce MoMo, which is a logic inspired by Hennessy–Milner Logic and the μ-calculus, that enables us to consider state properties in a distributed environment and the impact of actions and movements over the different sites. MoMo operators are interpreted over MLTSs and both MLTSs and MoMo are used to provide a semantic framework to describe two basic calculi for mobile computing, namely μKlaim and the asynchronous π-calculus
Multi labelled transition systems: a semantic framework for nominal calculi
No full textAction Labelled transition systems (LTS) have proved to be a fundamental model for describing and proving properties of concurrent systems. In this paper, Multiple Labelled Transition Systems (MLTS) are introduced as generalizations of LTS that permit dealing also with systems features that are becoming more and more important when considering languages and models for network aware programming. MLTS permit describing not only the actions systems can perform but also system's resources usage and their handling (creation, revelation ...) of names. To show adeguacy of our proposal we show how MLTS can be used to describe the operational semantics of one of the most studied calculus for mobility: the asynchronous [pi]-calculus
Online User Behavioural Modeling with Applications to Price Steering
Full text linkPrice steering is the practice of ?changing the order of search results to highlight specific products? and products prices. In this paper, we show an initial investigation to quantify the price steering level in search results shown to different kind of users on Google Shopping. We mimic the category of affluent users. Affluent users visit websites offering expensive services, search for luxury goods and always click on the most costly items results at Google Shopping. The goal is checking if users trained in specific ways get different search results, based on the price of the products in the results. Evaluation is based on well known metrics to measure page results differences and similarities. Experiments are automised, rendering large-scale investigations feasible. Results of our experiments, based on a preliminary experimental setting, show that users trained on some particular topics are not always influenced by previous search and click activities. However, different trained users actually achieve different search results, thus paving the way for further investigation
Using the Adxiomatic Presentation of Behavioural Equivalences for Manipulating CCS Specifications
No full textAn interactive system for proving properties of CCS specifications is described. This system allows users to take advantage of all three views of CCS semantics (the transitions, the operationally defined equivalences and the axioms) and to define their own verification strategies for moving from one view to another. The system relies on term rewriting techniques and manipulates only the symbolic representation of specifications without resorting to any other kind of internal representation
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