8,383 research outputs found
Service discovery and negotiation with COWS
To provide formal foundations to current (web) services technologies, we put forward using COWS, a process calculus for specifying, combining and analysing services, as a uniform formalism for modelling all the relevant phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, deployment and execution. In this paper, we show that constraints and operations on them can be smoothly incorporated in COWS, and propose a disciplined way to model multisets of constraints and to manipulate them through appropriate interaction protocols. Therefore, we demonstrate that also QoS requirement specifications and SLA achievements, and the phases of dynamic service discovery and negotiation can be comfortably modelled in COWS. We illustrate our approach through a scenario for a service-based web hosting provider
Meta SOS - A Maude Based SOS Meta-Theory Framework
Meta SOS is a software framework designed to integrate the results from the
meta-theory of structural operational semantics (SOS). These results include
deriving semantic properties of language constructs just by syntactically
analyzing their rule-based definition, as well as automatically deriving sound
and ground-complete axiomatizations for languages, when considering a notion of
behavioural equivalence. This paper describes the Meta SOS framework by
blending aspects from the meta-theory of SOS, details on their implementation
in Maude, and running examples.Comment: In Proceedings EXPRESS/SOS 2013, arXiv:1307.690
Programming Languages for Distributed Computing Systems
When distributed systems first appeared, they were programmed in traditional sequential languages, usually with the addition of a few library procedures for sending and receiving messages. As distributed applications became more commonplace and more sophisticated, this ad hoc approach became less satisfactory. Researchers all over the world began designing new programming languages specifically for implementing distributed applications. These languages and their history, their underlying principles, their design, and their use are the subject of this paper. We begin by giving our view of what a distributed system is, illustrating with examples to avoid confusion on this important and controversial point. We then describe the three main characteristics that distinguish distributed programming languages from traditional sequential languages, namely, how they deal with parallelism, communication, and partial failures. Finally, we discuss 15 representative distributed languages to give the flavor of each. These examples include languages based on message passing, rendezvous, remote procedure call, objects, and atomic transactions, as well as functional languages, logic languages, and distributed data structure languages. The paper concludes with a comprehensive bibliography listing over 200 papers on nearly 100 distributed programming languages
Working notes of the KI \u2796 Workshop on Agent Oriented Programming and Distributed Systems
Agent-oriented techniques are likely to be the next significant breakthrough in software development process. They provide a uniform approach throughout the analysis, design and implementation phases in the development life cycle. Agent-oriented techniques are a natural extension to object-oriented techniques, but while there is a whole pIethora of analysis and design methods in the object-oriented paradigm, very little work has been reported on design and analysis methods in the agent-oriented community. After surveying and examining a number of well-known object-oriented design and analysis methods, we argue that none of these methods, provide the adequate model for the design and analysis of multi-agent systems. Therefore, we propose a new agent-specific methodology that is based on and builds upon object-oriented methods. We identify three major models that need to be build during the development of multi-agent applications and describe the process of building these models
On component-oriented access control in lightweight virtualized server environments
2017 Fall.Includes bibliographical references.With the advancements in contemporary multi-core CPU architectures and increase in main memory capacity, it is now possible for a server operating system (OS), such as Linux, to handle a large number of concurrent services on a single server instance. Individual components of such services may run in different isolated runtime environments, such as chrooted jails or related forms of OS-level containers, and may need restricted access to system resources and the ability to share data and coordinate with each other in a regulated and secure manner. In this dissertation we describe our work on the access control framework for policy formulation, management, and enforcement that allows access to OS resources and also permits controlled data sharing and coordination for service components running in disjoint containerized environments within a single Linux OS server instance. The framework consists of two models and the policy formulation is based on the concept of policy classes for ease of administration and enforcement. The policy classes are managed and enforced through a Lightweight Policy Machine for Linux (LPM) that acts as the centralized reference monitor and provides a uniform interface for regulating access to system resources and requesting data and control objects. We present the details of our framework and also discuss the preliminary implementation and evaluation to demonstrate the feasibility of our approach
Timed Soft Concurrent Constraint Programs: An Interleaved and a Parallel Approach
We propose a timed and soft extension of Concurrent Constraint Programming.
The time extension is based on the hypothesis of bounded asynchrony: the
computation takes a bounded period of time and is measured by a discrete global
clock. Action prefixing is then considered as the syntactic marker which
distinguishes a time instant from the next one. Supported by soft constraints
instead of crisp ones, tell and ask agents are now equipped with a preference
(or consistency) threshold which is used to determine their success or
suspension. In the paper we provide a language to describe the agents behavior,
together with its operational and denotational semantics, for which we also
prove the compositionality and correctness properties. After presenting a
semantics using maximal parallelism of actions, we also describe a version for
their interleaving on a single processor (with maximal parallelism for time
elapsing). Coordinating agents that need to take decisions both on preference
values and time events may benefit from this language. To appear in Theory and
Practice of Logic Programming (TPLP)
SICStus MT - A Multithreaded Execution Environment for SICStus Prolog
The development of intelligent software agents and other
complex applications which continuously interact with their
environments has been one of the reasons why explicit concurrency has
become a necessity in a modern Prolog system today. Such applications
need to perform several tasks which may be very different with respect
to how they are implemented in Prolog. Performing these tasks
simultaneously is very tedious without language support.
This paper describes the design, implementation and evaluation of a
prototype multithreaded execution environment for SICStus Prolog. The
threads are dynamically managed using a small and compact set of
Prolog primitives implemented in a portable way, requiring almost no
support from the underlying operating system
The exploitation of parallelism on shared memory multiprocessors
PhD ThesisWith the arrival of many general purpose shared memory multiple processor
(multiprocessor) computers into the commercial arena during the mid-1980's, a
rift has opened between the raw processing power offered by the emerging
hardware and the relative inability of its operating software to effectively deliver
this power to potential users. This rift stems from the fact that, currently, no
computational model with the capability to elegantly express parallel activity is
mature enough to be universally accepted, and used as the basis for programming
languages to exploit the parallelism that multiprocessors offer. To add to this,
there is a lack of software tools to assist programmers in the processes of designing
and debugging parallel programs.
Although much research has been done in the field of programming languages,
no undisputed candidate for the most appropriate language for programming
shared memory multiprocessors has yet been found. This thesis examines why this
state of affairs has arisen and proposes programming language constructs,
together with a programming methodology and environment, to close the ever
widening hardware to software gap.
The novel programming constructs described in this thesis are intended for use
in imperative languages even though they make use of the synchronisation
inherent in the dataflow model by using the semantics of single assignment when
operating on shared data, so giving rise to the term shared values. As there are
several distinct parallel programming paradigms, matching flavours of shared
value are developed to permit the concise expression of these paradigms.The Science and Engineering Research Council
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