82,217 research outputs found
Towards a Tool-based Development Methodology for Pervasive Computing Applications
Despite much progress, developing a pervasive computing application remains a
challenge because of a lack of conceptual frameworks and supporting tools. This
challenge involves coping with heterogeneous devices, overcoming the
intricacies of distributed systems technologies, working out an architecture
for the application, encoding it in a program, writing specific code to test
the application, and finally deploying it. This paper presents a design
language and a tool suite covering the development life-cycle of a pervasive
computing application. The design language allows to define a taxonomy of
area-specific building-blocks, abstracting over their heterogeneity. This
language also includes a layer to define the architecture of an application,
following an architectural pattern commonly used in the pervasive computing
domain. Our underlying methodology assigns roles to the stakeholders, providing
separation of concerns. Our tool suite includes a compiler that takes design
artifacts written in our language as input and generates a programming
framework that supports the subsequent development stages, namely
implementation, testing, and deployment. Our methodology has been applied on a
wide spectrum of areas. Based on these experiments, we assess our approach
through three criteria: expressiveness, usability, and productivity
Fractal patterns in fractionated spacecraft
Multi spacecraft architectures have been addressed in response to the demand for flexible architectures with high reliability and reduced costs compared to traditional monolithic spacecraft. A task that can be easily carried out by this kind of systems is the deployment of distributed antennas; these are composed of, typically, receiving elements carried on-board multiple spacecraft in precise formation. In this paper decentralised control means, based on artificial potential functions, together with a fractal-like connection network, are used to produce the autonomous and verifiable deployment and formation control of a swarm of spacecraft into a fractal-like pattern. The effect of using fractal-like routing of control data within the spacecraft generates complex formation shape patterns, while simultaneously reducing the amount of control information required to form such complex formation shapes. Furthermore, the techniques used ensure against swarm fragmentation, while exploiting communication channels anyway needed in a fractionated architecture. In particular, the superposition of potential functions operating at multiple levels (single agents, subgroups of agents, groups of agents) according to a self-similar adjacency matrix produces a fractal-like final deployment with the same stability property on each scale. Considering future high-precision formation flying and control capabilities, this paper considers, for the first time and as an example of a fractionated spacecraft, a decentralised multi-spacecraft fractal shaped antenna. A fractal antenna pattern provides multiple resonance peaks, directly related to the ratios of its characteristic physical lengths. Such a scenario would significantly improve the level of functionality of any multi-spacecraft synthetic aperture antenna system. Furthermore, multi-spacecraft architecture exploiting particular inter agent spacing can be considered to investigate multi-scale phenomena in areas such as cosmic radiation and space plasma physics. Both numerical simulations and analytic treatment are carried out demonstrating the feasibility of deploying and controlling a fractionated fractal antenna in space through autonomous decentralised means
Using P3P in a web services-based context-aware application platform
This paper describes a proposal for a privacy control architecture to be applied in the WASP project. The WASP project aims to develop a context-aware service platform on top of 3G networks, using web services technology. The proposed privacy control architecture is based on the P3P privacy policy description standard defined by W3C. The paper identifies extensions to P3P and its associated preference expression language APPEL that are needed to operate in a context-aware environment
Modelling the GSM handover protocol in CommUnity
CommUnity is a formal approach to software architecture. It has a precise, yet intuitive mathematical semantics based on category theory. It supports, at the methodological level, a clear separation between computation, coordination, and distribution (including mobility). It provides a simple state-based language for describing component behaviour that is inspired by Unity and Interacting Processes. It also addresses composition as a first class concern and accounts for the emergence of global system properties from interconnections. This paper describes the approach and available tool support by modelling essential aspects of the GSM handover protocol. We also sketch a framework that we are implementing for the distributed execution of such specifications using Klava, a Java library for mobile agent systems based on tuple spaces
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