Hybrid-Fixing:上下文一致性错误的正确修复

在普适计算中,上下文持续快速变化,上下文感知应用根据上下文变化自动调整自身的行为以作出适应.然而,由于不可预测和控制的环境噪声以及环境动态变化等诸多因素的影响,环境上下文会发生一致性错误,从而导致应用表现异常甚至失效.为了解决这些问题,上下文一致性错误需要被自动并正确地修复,现基于已有工作提出了一项新的修复技术hybrid-fixing,它结合了对一致性约束的静态分析和修复动作的动态产生,即使一致性约束内部存在复杂依赖关系,也能确保所生成的修复用例必然正确.实验结果表明,这项修复技术大幅提高了一致性约束内部存在复杂依赖关系下一致性错误修复的成功率,并只花费了很小的时间开销.     

普适计算环境下基于中间件的上下文质量管理框架研究

随着信息技术的快速发展,分布式计算技术逐渐向普适计算技术演化,从而达到信息空间和物理空间融合的最终目标,为用户提供普适的智能化服务。为了达到这个目标,一个主要的困难就是如何有效地连续监测、才甫获与解释环境相关的上下文信息来确保精确的上下文感知性。很多研究者已先后投身于上下文感知的普适应用的研究工作中,但大多数往往直接针对原始上下文进行处理,没有考虑上下文质量(QoC)的影响。因此,提出了一种基于中间件的上下文质量管理框架,即通过上下文的质量门阂管理、重复与不一致的上下文丢弃等不同层次的控制机制,为上下文感知服务和应用用户提供有效而可靠的上下文服务。     

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。     

面向普适计算的动态自适应中间件模型

为了提高普适计算系统的开发效率, 设计了一个基于OSGi框架的动态普适计算中间件模型. 该中间件模型以OSGi框架为基础, 建立移动管理器管理用户和服务的移动, 利用上下文管理器来管理上下文, 动态调整自己的行为, 支持上下文感知应用. 通过标准的接口实现各种异构普适设备间的互操作性. 实验结果表明该中间件能够满足通用普适计算环境的要求, 对于普适计算系统的开发具有一定的借鉴意义.     

支持上下文感知的构件适配模型研究

为了对普适环境下的构件化应用提供支持,扩展传统的构件适配技术,在上下文感知中间件的基础上,提出支持上下文感知的构件适配模型CACAM和构件适配算法CACA,实现对环境、用户上下文的动态感知和重配置。实验结果表明,该模型能够有效地实现普适计算环境下基于上下文感知的构件适配。     

基于上下文感知的普适计算辅助教学设计与实现

随着计算机技术的发展,普适计算作为一种新的计算模式孕育而生。基于普适计算的应用技术能为使用人群提供主动的,个性化的服务,这一特点可以极大地改善现有计算机辅助教学过程中一些固有缺陷。文中分析了普适计算在教学中的意义,研究了近年来国内外在上下文感知领域的探索,指出了普适计算技术在实验教学中的优越性,设计了一个基于上下文感知的普适计算辅助教学实验。     

基于搜索的上下文一致性错误处理

近年来,随着智能设备的普及和传感技术的发展,上下文感知程序的应用越来越广泛。但是由于环境噪声难以预测和控制,程序所获得的上下文经常存在一致性错误。处理这类错误的方法很多,但大都忽视了两方面的问题:1)不同一致性约束之间存在相互干扰;2)处理这类错误的操作本身可能对程序的正常运行造成负面影响。以处理这两方面的问题为目标,提出了一种新的基于搜索的上下文一致性错误处理方法,亦即既设计出一个搜索空间来查找避免约束间相互干扰和对程序产生负面影响的解,又采用了一种增量式评估方案来加速搜索的效率。经实验评估,新方法能够在很短的时间内达到非常接近最优解的效果。     

普适计算环境中上下文模型的建立

普适计算作为第三代计算方式已经成为科学研究的前沿,上下文作为普适计算中最为重要研究方向之一,对普适计算的研究和发展有着大力地推动作用.就建立普适计算环境上下文模型进行了分析和讨论,对上下文的数据和通信方式也进行了分析,为上下文的实际应用提供一些理论基础准备.     

上下文不一致性检测及消除的研究

在普适计算环境下,由于获得的上下文信息存在不一致性,使得上下文感知应用无法正常进行响应。研究了普适计算环境下的上下文不一致性的检测及消除,针对其提出了基于置信度数据库的反馈机制,并且丰富和扩展了上下文不一致性的消除算法。实现了相关算法,并通过实验给出了各个算法的效率和正确性的比较。     

基于RFID普适计算环境的形式化上下文模型

提出了一个适合普适计算环境的、基于本体的形式化的上下文感知模型。该模型使用本体描述语言OWL描述上下文，采用层次化的设计方法，提高了上下文表达能力和快速上下文原型。为普适计算的上下文建模和应用、上下文重用和建立面向普适计算环境的软件基础设施提供了一种可行的方法。     

Suppressing detection of inconsistency hazards with pattern learning

Context: Inconsistency detection and resolution is critical for context-aware applications to ensure their normal execution. Contexts, which refer to pieces of environmental information used by applications, are checked against consistency constraints for potential errors. However, not all detected inconsistencies are caused by real context problems. Instead, they might be triggered by improper checking timing. Such inconsistencies are ephemeral and usually harmless. Their detection and resolution is unnecessary, and may even be detrimental. We name them inconsistency hazards.Objective: Inconsistency hazards should be prevented from being detected or resolved, but it is not straightforward since their occurrences resemble real inconsistencies. In this article, we present SHAP, a pattern-learning based approach to suppressing the detection of such hazards automatically.Method: Our key insight is that detection of inconsistency hazards is subject to certain patterns of context changes. Although such patterns can be difficult to specify manually, they may be learned effectively with data mining techniques. With these patterns, we can reasonably schedule inconsistency detections.Results: The experimental results show that SHAP can effectively suppress the detection of most inconsistency hazards (over 90%) with negligible overhead.Conclusions: Comparing with other approaches, our approach can effectively suppress the detection of inconsistency hazards, and at the same time allow real inconsistencies to be detected and resolved timely.     

XCML: providing context-aware language extensions for the specification of multi-device web applications

There is a vast body of research dealing with the development of context-aware web applications that can adapt to different user, platform and device contexts. However, the range and growing diversity of new devices poses two significant problems to existing approaches. First, many techniques require a number of additional design processes and modelling steps before applications can be adapted. Second, the new generation of platforms and technologies underlying these devices as well as upcoming web standards HTML5 and CSS3 have partly changed the way in which web applications are implemented nowadays and often limit the way in which they can be adapted. In this paper, we present XCML as one example of a domain-specific language that tightly integrates context-aware concepts and adaptivity mechanisms to support developers in the specification and implementation of multi-channel web applications. In contrast to most existing approaches, the objective is to use a more lightweight approach to adaptation that can dynamically evolve and support new requirements as they emerge. Our solution builds on versioning principles in combination with a context matching process based on a declaration of context-dependent variants of content, navigation and presentation in terms of context expressions at different levels of granularity that are specific to the application. To support this, a formally defined context algebra is used to parse and resolve the context expressions at compile-time and to determine the best-matching variants with respect to the client context at run-time. We present the language concepts and a possible execution environment together with context-aware developer tools for the authoring and testing of adaptive features and behaviour. We also report on two case studies: the first shows how our general approach allows for integration with existing technologies to leverage advanced context-aware mechanisms in applications developed using other platforms and languages and the second how existing web interfaces can be systematically extended to support new adaptation scenarios.     

A portable toolkit for supporting end-user personalization and control in context-aware applications

A context-aware application in the pervasive computing environment provides intuitive user centric services using implicit context cues. Personalization and control are important issues for this class of application as they enable end-users to understand and configure the behavior of an application. However most development efforts for building context-aware applications focus on the sensor fusion and machine learning algorithms to generate and distribute context cues that drive the application with little emphasis on user-centric issues. We argue that, to elevate user experiences with context-aware applications, it is very important to address these personalization and control issues at the system interface level in parallel to context centric design. Towards this direction, we present Persona, a toolkit that provides support for extending context-aware applications with end-user personalization and control features. Specifically, Persona exposes a few application programming interfaces that abstract end-user customization and control mechanisms and enables developers to integrate these user-centric aspects with rest of the application seamlessly. There are two primary advantages of Persona. First, it can be used with various existing middlewares as a ready-to-use plug-in to build customizable and controllable context-aware applications. Second, existing context-aware applications can easily be augmented to provide end-user personalization and control support. In this paper, we discuss the design and implementation of Persona and demonstrate its usefulness through the development and augmentation of a range of common context-aware applications.     

Model-based system configuration approach for Internetware

Internetware applications are emerging and being widely used. They can adapt their behavior based on environmental contexts and deliver smart services. These contexts can be subject to various noises, which cause them to be inaccurate, incomplete, or even to conflict with each other. This is known as context inconsistency problem. Context inconsistency can trigger unexpected behavior to applications, and therefore should be prevented. One promising approach is to check contexts against consistency constraints so as to detect the occurrences of context inconsistency at runtime. Existing techniques have attempted different ways to improve the checking efficiency or effectiveness with different trade-offs in space overhead or communication cost. However, none of them has exploited multi-core computing capability to systematically improve the checking efficiency. In this paper, we propose a novel concurrent checking technique Con-C to efficiently detect inconsistencies in huge volumes of dynamic contexts. Con-C derives checking subtasks for each consistency constraint based on its structure and semantics. It achieves this in a fully automated way, and at the same time can guarantee its derived checking subtasks to be persistently balanced. We evaluated Con-C by controlled experiments through a large-scale real-world application. It reported promising results that Con-C improved the checking efficiency by extra 57.0%, in addition to what had been gained by incremental checking.     

CARISMA: context-aware reflective middleware system for mobile applications

Mobile devices, such as mobile phones and personal digital assistants, have gained wide-spread popularity. These devices will increasingly be networked, thus enabling the construction of distributed applications that have to adapt to changes in context, such as variations in network bandwidth, battery power, connectivity, reachability of services and hosts, etc. In this paper, we describe CARISMA, a mobile computing middleware which exploits the principle of reflection to enhance the construction of adaptive and context-aware mobile applications. The middleware provides software engineers with primitives to describe how context changes should be handled using policies. These policies may conflict. We classify the different types of conflicts that may arise in mobile computing and argue that conflicts cannot be resolved statically at the time applications are designed, but, rather, need to be resolved at execution time. We demonstrate a method by which policy conflicts can be handled; this method uses a microeconomic approach that relies on a particular type of sealed-bid auction. We describe how this method is implemented in the CARISMA middleware architecture and sketch a distributed context-aware application for mobile devices to illustrate how the method works in practice. We show, by way of a systematic performance evaluation, that conflict resolution does not imply undue overheads, before comparing our research to related work and concluding the paper.     

Model-driven development of composite context-aware web applications

Context-awareness constitutes an essential aspect of services, especially when interaction with end-users is involved. In this paper a solution for the context-aware development of web applications consisting of web services is presented. The methodology proposes a model based approach and advocates in favour of a complete separation of the web application functionality from the context adaptation at all development phases (analysis, design, implementation). In essence, context adaptation takes place on top of and is transparent to the web application business functionality. Starting from UML diagrams of independent web services and respective UML context models, our approach can produce a functional composite context-aware application. At execution level this independence is maintained through an adaptation framework based on message interception.     

Context data management: an architectural framework for context-aware services

Mobile devices are equipped with increasing processing power and sensing capabilities, and mobile services can benefit from these features to provide a more personalized and context-aware experience to final users. To efficiently collect and deliver context information, a proper architecture is required, where heterogeneous context information can be processed to provide higher-level context information, context data are represented uniformly, and applications can process context data with high-level queries. This paper fulfils this goal of interoperability and domain independence by defining a framework for context data management relying on open standards (XMPP and REST), acting as an enabler for third-party context-aware applications; other main novelties of our work are the definition of a ContextML for standard context data representation, and a Context Query Language (CQL) to access context information based on high-level data filtering.     

Modelling and Adapting to Context

One of the hardest points in context-aware applications is deciding what reactions a system has to a certain context. In this paper, we introduce an architecture used in two context-aware museum guides. We discuss how the context is modelled and we briefly present a rule-based mechanism to trigger system actions. A rule-based system offers the flexibility required to be context-sensitive in the broadest sense since many context features can be considered and evaluated at the same time. This architecture is very flexible and easily supports a fast prototyping approach.     

Paraconsistency and Plausible Argumentation in Generative Grammar: A Case Study

While the analytical philosophy of science regards inconsistent theories as disastrous, Chomsky allows for the temporary tolerance of inconsistency between the hypotheses and the data. However, in linguistics there seem to be several types of inconsistency. The present paper aims at the development of a novel metatheoretical framework which provides tools for the representation and evaluation of inconsistencies in linguistic theories. The metatheoretical model relies on a system of paraconsistent logic and distinguishes between strong and weak inconsistency. Strong inconsistency is destructive in that it leads to logical chaos. In contrast, weak inconsistency may be constructive, because it is capable of accounting for the simultaneous presence of seemingly incompatible structures. However, paraconsistent logic cannot grasp the dynamism of the emergence and resolution of weak inconsistencies. Therefore, the metatheoretical approach is extended to plausible argumentation. The workability of this metatheoretical model is tested with the help of a detailed case study on an analysis of discontinuous constituents in Government-Binding Theory.