基于普适计算的服务发现系统设计

在普适计算环境下,服务是动态变化的,而服务发现技术能够在动态变化的普适计算环境中动态查找、定位所需要的服务,是解决普适计算环境异构性、实现不同应用集成的有效途径.介绍了服务的语义描述语言OWL-S,用于对服务进行描述,然后设计并实现了一个普适计算下的服务发现系统.同时,详细介绍了服务请求时进行服务匹配使用的匹配算法.通过增加语义信息,达到服务发布者和请求者可以实现语义层次的匹配,提高了服务的查准率和查全率.     

普适计算中间件技术的研究与进展

当前，普适计算已经成为计算机科学中一个极具活力和影响力的研究领域。普适计算环境规模很大并且具有高度异构性，如网络架构的异构性、硬件平台的异构性、操作系统的异构性、应用服务的异构性等，而普适计算中间件技术可以解决异构性和跨平台特征，提供不同服务的集成应用，因此成为普适计算中的一个研究热点。基于此，本文对于目前国外关于普适计算中间件技术的研究现状做了一个总结；通过分析和比较，给出了普适计算中间件的设计原则；探讨了普适计算中间件技术的未来发展方向。     

普适计算：人本计算

普适计算强调以人为本的计算思想，它主张计算应迎合人的习性，自主地与使用者产生互动，使用户能集中精力于所要完成的任务。在普适计算环境下，计算将融入到人们的日常生活之中，使人们能够随时随地无妨碍地获得计算和信息服务。综述了普适计算的发展历史、现状和研究热点，分析和讨论了普适计算的概念和特性，最后对目前一些具有代表性的普适计算研究项目进行了简要的介绍和分析。     

普适计算环境下信任机制的研究进展

在普适计算环境下,各种资源、设备和用户均是高度动态变化的,服务请求者和服务提供者一般互相不了解,因此普适计算环境下各陌生实体间的相互认证是传统的基于身份的认证机制无法解决的.普适计算信任建模机制可以解决普适计算环境下的不确定性问题,为陌生实体间建立信任关系,因此成为普适计算中的一个研究热点.基于此,本文对于目前国外关于普适计算信任建模机制的研究现状做了一个总结,通过分析和比较,给出了普适计算信任建模的设计原则,探讨了普适计算信任建模问题的未来发展方向.     

移动普适环境中支持QoS控制的安全框架研究

基于对移动普适计算环境所面临的安全威胁的分析,从用户,网络和服务提供商3个方面总结了移动普适计算环境的特殊安全需求,并提出一种适用于移动普适计算环境且支持QoS(quality of service)控制的安全框架.对该框架的相关功能操作和工作时序进行了介绍,并着重研究和实现了安全框架中的QoS控制流程.通过此框架,移动互联网设备用户可以随时随地访问移动普适计算环境并获得高质量的安全服务.     

面向LBS的服务匹配方法研究

随着普适计算的不断深入发展,基于位置的服务也逐渐成为应用研究的重要方面。服务发现技术成为核心问题,而服务匹配就是重中之重,也是现在研究的热点问题。在对用户提供服务时,不仅要提高服务质量,而且要充分考虑用户的偏好。在面向位置服务领域分析与比较了现有的主流服务发现协议,并基于分析比较,提出了一种新的服务匹配方法,它通过分层匹配,以及充分考虑用户喜好程度来提高服务匹配成功率,从而达到提高服务质量的目的。     

普适计算环境下的服务发现协议

为了更好地了解现有服务发现协议,提出普适环境下的服务发现协议评价指标,根据网络类型和服务信息存储方式对不同网络环境中、不同体系结构下的典型服务发现协议进行分类和比较,给出无线自组织环境下5种服务发现协议依据该评价指标进行定性比较的结果。     

一种基于情境的语义Web服务发现方法

在普适计算环境下,如何结合情境信息以发现满足用户需求的服务,是目前Web服务研究的一个关键问题.提出一种基于情境的Web服务发现框架,采用本体进行情境建模,利用用户反馈信息进行权重计算,并给出了一个基于相似度的语义Web服务的匹配算法.最后通过实验验证了该方法的有效性.     

一种基于上下文协商的动态服务组合方法

普适计算的计算环境和交互信息动态变化,为了提供适时适地的服务,服务组合除了满足用户的需求之外,还要适应环境的变化.以面向普适计算的分布式文档管理系统为例,提出一种基于上下文协商的动态服务组合方法,适应普适计算环境下资源动态变化的特点,同时满足用户对服务的需求.首先定义上下文和带有上下文信息的服务模型;然后给出服务和设备以及服务和用户之间的上下文协商约束条件,根据约束条件提出基本算法实现服务动态组合,并对基本算法进行优化;最后通过原型系统和实验验证算法的性能和有效性,并通过实验数据分析上下文对于服务组合的影响.实验数据说明:提出的方法能够应用在普适计算环境中上下文敏感的服务组合问题上,提高服务组合的动态适应性和网络资源利用率.     

普适计算服务组合技术综述*

普适计算环境因其所具有的动态性、资源约束性和上下文感知性使其服务的组合面临特有的问题和挑战。服务匹配和选择、服务协调和管理、错误检测和修复是解决普适计算服务组合的三个关键技术。比较了普适计算服务匹配和选择的方法,重点分析了服务协调和管理的手段,给出了错误检测和修复的方法,最后提出解决普适计算服务组合的建议。     

A semantic service discovery approach for ubiquitous computing

Services in the ubiquitous computing are heterogeneous in nature. To be pervasive, these services should be defined in terms of their functionality and capabilities rather than the meaningless Universally Unique IDentifiers (UUIDs) or types of services. With that, clients can access the proper service based on semantic requests, rather then a pre-configured profile. In this paper, we study the requirements for semantic query to be feasible in service discovery processes. Current discovery protocols and the concept of semantics are brought together to construct a framework to realize the semantic service discovery for ubiquitous computing. Many issues are discussed in relation to service discovery topologies, ontology languages, and semantic query languages.     

服务发现技术中安全问题的解决方案

服务发现技术是指网络中结点自动获取其它结点提供的服务的相关信息的机制。随着普及计算技术的发展,服务发现越来越显示出其重要性。服务发现涉及到多方面的问题。而安全问题就是其中的一个关键问题。本文对几种典型的服务发现系统中服务发现的安全问题的解决方案作了介绍和分析,以促进更加安全的服务发现技术的开发。     

EASY: Efficient semAntic Service discoverY in pervasive computing environments with QoS and context support

Pervasive computing environments are populated with networked software and hardware resources providing various functionalities that are abstracted, thanks to the Service Oriented Architecture paradigm, as services. Within these environments, service discovery enabled by service discovery protocols (SDPs) is a critical functionality for establishing ad hoc associations between service providers and service requesters. Furthermore, the dynamics, the openness and the user-centric vision aimed at by the pervasive computing paradigm call for solutions that enable rich, semantic, context- and QoS-aware service discovery. Although the semantic Web paradigm envisions to achieve such support, current solutions are hardly deployable in the pervasive environment due to the costly underlying semantic reasoning with ontologies. In this article, we present EASY to support efficient, semantic, context- and QoS-aware service discovery on top of existing SDPs. EASY provides EASY-L, a language for semantic specification of functional and non-functional service properties, as well as EASY-M, a corresponding set of conformance relations. Furthermore, EASY provides solutions to efficiently assess conformance between service capabilities. These solutions are based on an efficient encoding technique, as well as on an efficient organization of service repositories (caches), which enables both fast service advertising and discovery. Experimental results show that the deployment of EASY on top of an existing SDP, namely Ariadne, enhancing it only with slight changes to EASY-Ariadne, enables rich semantic, context- and QoS-aware service discovery, which furthermore performs better than the classical, rigid, syntactic matching, and improves the scalability of Ariadne.     

Context-based caching and routing for P2P web service discovery

In modern heterogeneous environments, such as mobile, pervasive and ad-hoc networks, architectures based on web services offer an attractive solution for effective communication and inter-operation. In such dynamic and rapidly evolving environments, efficient web service discovery is an important task. Usually this task is based on the input/output parameters or other functional attributes, however this does not guarantee the validity or successful utilization of retrieved web services. Instead, non-functional attributes, such as device power features, computational resources and connectivity status, that characterize the context of both service providers and consumers play an important role to the quality and usability of discovery results. In this paper we introduce context-awareness in web service discovery, enabling the provision of the most appropriate services at the right location and time. We focus on context-based caching and routing for improving web service discovery in a mobile peer-to-peer environment. We conducted a thorough experimental study, using our prototype implementation based on the JXTA framework, while simulations are employed for testing the scalability of the approach. We illustrate the advantages that this approach offers, both by evaluating the context-based cache performance and by comparing the efficiency of location-based routing to broadcast-based approaches. Recommended by: Zakaria Maamar     

DaaS: Cloud-based mobile Web service discovery

The proliferation of smartphones and the recent advancement in ubiquitous wireless access have made mobile Web services more possible than ever before. However, finding relevant Web services that can match requests and fit user context remains a major concern. The challenges facing Web service discovery are further magnified by the stringent constraints of mobile devices and the inherit complexity of wireless heterogeneous networks. Cloud computing, with its flexible design and theoretically unlimited computing resources, is a viable approach to bootstrapping Web service discovery. The cloud can build bridges between mobile devices, as a convenient ubiquitous interface, and a backbone infrastructure with abundant computing resources. This paper introduces “Discovery as a service (Daas)”, a novel cloud-based discovery framework that addresses the core components of mobile Web service discovery. The DaaS framework lays the foundation of efficient mobile Web service discovery that takes into consideration user preferences and context. The experimental validation and performance evaluation demonstrate that DaaS can effectively rank relevant services according to the various user context and preferences, in addition to enhancing the precision of the discovered services. The prototype also shows that Web service clustering for discovery significantly improves the overall response time, while the cloud maintains scalability according to prespecified performance criteria.     

一种普及计算环境中的基础设施：PvCGrid

随着计算机技术的发展，人们希望能方便地享用计算能力和信息服务，但是由于计算设备的多样性和设备之间多传输协议的多样性，资源的描述、发现和使用方式的差异，资源之间协作缺乏统一的标准，造成了使用计算设备的障碍。该文提出了一种在普及计算环境中的基础设施——PvCGrid，实现了多种传输协议的管理、设备和服务的发现，提供了用户可定制的组合服务的功能，使得用户可以发现和使用网络中的资源，并且可以根据发现的资源，定制出更加复杂的应用，该基础设施为普及计算提供了互连互通、资源共享和协同服务的技术支持。     

服务发现技术中的服务描述和服务匹配技术

普及计算环境中的设备和应用需要通过服务发现来获得其它设备和应用所提供的服务。在服务发现技术中,服务描述、需求描述和服务匹配是迫切需要解决的关键问题。但由于服务和需求的多样性和复杂性,以及普及计算环境的动态性和异构性,使这些问题更加困难和复杂。所以,寻找一种灵活高效而又准确的方式来进行服务描述、需求描述,进而进行服务匹配,具有非常重要的意义。对现有多种服务发现系统中的服务描述需求描述和服务匹配技术进行比较分析,指出了现有解决方案的一些不足,并对未来的研究进行了展望。     

COCOA: COnversation-based service COmposition in pervAsive computing environments with QoS support

Pervasive computing environments are populated with networked services, i.e., autonomous software entities, providing a number of functionalities. One of the most challenging objectives to be achieved within these environments is to assist users in realizing tasks that integrate on the fly functionalities of the networked services opportunely according to the current pervasive environment. Towards this purpose, we present COCOA, a solution for COnversation-based service COmposition in pervAsive computing environments with QoS support. COCOA provides COCOA-L, an OWL-S based language for the semantic, QoS-aware specification of services and tasks, which further allows the specification of services and tasks conversations. Moreover, COCOA provides two mechanisms: COCOA-SD for the QoS-aware semantic service discovery and COCOA-CI for the QoS-aware integration of service conversations towards the realization of the user task’s conversation. The distinctive feature of COCOA is the ability of integrating on the fly the conversations of networked services to realize the conversation of the user task, by further meeting the QoS requirements of user tasks. Thereby, COCOA allows the dynamic realization of user tasks according to the specifics of the pervasive computing environment in terms of available services and by enforcing valid service consumption.     

一种普适环境下面向服务的事务处理模型

普适环境具有高移动、极端异构、高自治和开放性的特点,普适环境下的服务组合因其突出的动态性问题,为保证对整个服务运行结果的可靠性和一致性,引入事务处理的机制来进行管理。提出一种在普适环境下面向服务的事务处理模型,在服务的发现、组合及运行中引入事务机制来协调管理,保证了服务组合的可靠一致性,并讨论了模型的系统架构和各模块组成,及应用场景。