An Adaptive Middleware for Context-Sensitive Communications for Real-Time Applications in Ubiquitous Computing Environments

Context-sensitivity is an important expected capability in applications in ubiquitous computing (ubicomp) environments. These applications need to use different contextual information from the user, host device, on board sensors, network, and the ambient environments to systematically adapt their actions. In addition, some context-sensitive applications may use specific contextual conditions to trigger impromptu and possibly short-lived interactions with applications in other devices. This property, referred to as context-sensitive or context-aware communications, allows applications to form short-range mobile ad hoc networks consisting of mobile and stationary devices, sensors, and other computing resources. Real-time applications, especially those having reactive behavior, running on embedded devices and requiring context-sensitive communications support, pose new challenges related to systematic representation of specific contexts, associations of contexts with real-time actions, timely context data collection and propagation, and transparent context-sensitive connection establishment. An object-based middleware can be effective to meet these challenges if such a middleware can provide a well-defined development framework as well as lightweight runtime services. In this paper, an adaptive and object-based middleware, called reconfigurable context-sensitive middleware (RCSM) is presented to facilitate context-sensitive communications in ubicomp environments. To facilitates context-sensitive communications, RCSM provides a context-aware interface definition language for specifying context-sensitive interfaces of real-time objects, an object container framework for generating interfaces-specific context-analyzers, and a context-sensitive object request broker for context-sensitive object discovery and impromptu connection management. RCSM is adaptive in the sense that depending on the context-sensitive behavior of the applications, it adapts its object discovery and connection management mechanisms.     

MobiPADS: a reflective middleware for context-aware mobile computing

Traditionally, middleware technologies, such as CORBA, Java RMI, and Microsoft's DCOM, have provided a set of distributed computing services that essentially abstract the underlying network services to a monolithic "black box." In a mobile operating environment, the fundamental assumption of middleware abstracting a unified distributed service for all types of applications operating over a static network infrastructure is no longer valid. In particular, mobile applications are not able to leverage the benefits of adaptive computing to optimize its computation based on current contextual situations. In this paper, we introduce the Mobile Platform for Actively Deployable Service (MobiPADS) system. MobiPADS is designed to support context-aware processing by providing an executing platform to enable active service deployment and reconfiguration of the service composition in response to environments of varying contexts. Unlike most mobile middleware, MobiPADS supports dynamic adaptation at both the middleware and application layers to provide flexible configuration of resources to optimize the operations of mobile applications. Within the MobiPADS system, services (known as mobilets) are configured as chained service objects to provide augmented services to the underlying mobile applications so as to alleviate the adverse conditions of a wireless environment.     

FollowMeLite：用于普适计算的轻量级中间件平台

普适计算的目标是让环境和计算资源紧密结合，以便更好地为人类服务。为达到这一目标，移动设备和嵌入式设备构成了环境中计算资源的重要组成部分。然而，由于移动设备和嵌入式设备的计算资源有限，网络连接的多样性和不稳定性以及软硬件的异构性，开发用于这些设备的上下文感知应用复杂并且费时，其根本原因是缺乏一个统一的平台支持。为解决这一问题，我们提出了一种用于普适计算的轻量级中间件平台，叫做FollowMeLite。FollowMeLite是整个FollowMe普适计算基础结构中的一部分。它构建在OSGi之上，集成了基于本体的上下文模型和基于工作流的应用模型以及用于适应多种网络连接的通讯服务。通过部署不同的组件模块，FollowMeLite可以方便的适用于多种应用环境。     

支持移动计算的反射式中间件

传统中间件基于黑盒的设计思想,缺乏必要的灵活性,无法适应复杂动态多变的移动计算环境。反射技术可以使应用程序在运行时检查中间件所提供的服务类型,动态的构造调用请求,适应变化的环境。文章研究了反射的相关概念,中间件技术,分析了移动计算的实际需求,提出了一个支持移动计算的反射中间件架构,支持环境感知、异步通信、动态重配置等。     

Data-centric middleware for context-aware pervasive computing

The complexity of developing and deploying context-aware pervasive-computing applications calls for distributed software infrastructures that assist applications to collect, aggregate, and disseminate contextual data. In this paper, we motivate a data-centric design for such an infrastructure to support context-aware applications. Our middleware system, Solar, treats contextual data sources as stream publishers. The core of Solar is a scalable and self-organizing peer-to-peer overlay to support data-driven services. We describe how different services can be systematically integrated on top of the Solar overlay and evaluate the resource discovery and data-dissemination services. We also discuss our experience and lessons learned when using Solar to support several implemented scenarios. We conclude that a data-centric infrastructure is necessary to facilitate both the development and deployment of context-aware pervasive-computing applications.     

EgoSpaces: facilitating rapid development of context-aware mobile applications

Today's mobile applications require constant adaptation to their changing environments, or contexts. Technological advances have increased the pervasiveness of mobile computing devices such as laptops, handhelds, and embedded sensors. The sheer amount of context information available for adaptation places a heightened burden on application developers as they must manage and utilize vast amounts of data from diverse sources. Facilitating programming in this data-rich environment requires a middleware that provides context information to applications in an abstract form. In this paper, we demonstrate the feasibility of such a middleware that allows programmers to focus on high-level interactions among programs and to employ declarative abstract context specifications in settings that exhibit transient interactions with opportunistically encountered components. We also discuss the novel context-aware abstractions the middleware provides and the programming knowledge necessary to write applications using it. Finally, we provide examples demonstrating the infrastructure's ability to support differing tasks from a wide variety of application domains.     

Pervaho: A specialized middleware for mobile context-aware applications

The concept of context-awareness offers a great potential for the future of mobile applications. In order to be developed in an optimal way, mobile context-aware applications need appropriate middleware services. This paper introduces Pervaho, an integrated middleware aimed specifically at supporting the development and testing of mobile context-aware applications. To illustrate the use of Pervaho, we walk through the development of a concrete mobile application and show how it can be built on top of Pervaho’s location-based publish/subscribe service. We also illustrate how a specialized mobility testing tool significantly simplifies the process of testing proximity-based semantics. We then present the implementation of Pervaho, which is based on a set of communication protocols geared at mesh networks. Finally, we provide a performance analysis of our implementation.     

A pluggable middleware architecture for developing context-aware mobile applications

The proliferation of powerful smartphone devices provides a great opportunity for context-aware mobile applications becoming mainstream. However, we argue that conventional software development techniques suffer because of the added complexity required for collecting and managing context information. This paper presents a component-based middleware architecture which facilitates the development and deployment of context-aware applications via reusable components. The main contribution of this approach is the combination of a development methodology with the middleware architecture, which together bring significant value to developers of context-aware applications. Further contributions include the following: The methodology utilizes separation of concerns, thus decreasing the developmental cost and improving the productivity. The design and implementation of context-aware applications are also eased via the use of reusable components, called context plug-ins. Finally, the middleware architecture facilitates the deployment and management of the context plug-ins in a resource-aware manner. The proposed methodology and middleware architecture are evaluated both quantitatively and qualitatively.     

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.     

Context-aware middleware for resource management in the wireless Internet

The provisioning of Web services over the wireless Internet introduces novel challenging issues for service design and implementation: from user/terminal mobility during service execution, to wide heterogeneity of portable access devices and unpredictable modifications in accessible resources. In this scenario, there are frequent provision-time changes in the context, defined as the logical set of accessible resources depending on client location, access terminal capabilities, and system/service management policies. The development of context-dependent services requires novel middlewares with full context visibility. We propose a middleware for context-aware resource management, called CARMEN, capable of supporting the automatic reconfiguration of wireless Internet services in response to context changes without any intervention on the service logic. CARMEN determines the context on the basis of metadata, which include declarative management policies and profiles for user preferences, terminal capabilities, and resource characteristics. In addition, CARMEN exploits the mobile agent technology to implement mobile middleware components that follow the provision-time movement of clients to support locally their customized service access. The proposed middleware shows how metadata and mobile agents can favor component reusability and automatic service reconfiguration, by reducing the development/ deployment complexity.     

MIMOSA: context-aware adaptation for ubiquitous web access

The ubiquitous computing scenario is characterized by heterogeneity of devices used to access services, and by frequent changes in the user’s context. Hence, adaptation according to the user’s context and the used devices is necessary to allow mobile users to efficiently exploit Internet-based services. In this paper, we present a distributed framework, named MIMOSA, that couples a middleware for context-awareness with an intermediary-based architecture for content adaptation. MIMOSA provides an effective and efficient solution for the adaptation of Internet services on the basis of a comprehensive notion of context, by means of techniques for aggregating context data from distributed sources, deriving complex contextual situations from raw sensor data, evaluating adaptation policies, and solving possible conflicts. The middleware allows programmers to modularly build complex adaptive services starting from simple ones, and includes tools for assisting the user in declaring her preferences, as well as mechanisms for detecting incorrect system behaviors due to a wrong choice of adaptation policies. The effectiveness and efficiency of MIMOSA are shown through the development of a prototype adaptive service, and by extensive experimental evaluations.     

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。     

Providing user context for mobile and social networking applications

The processing capabilities of mobile devices coupled with portable and wearable sensors provide the basis for new context-aware services and applications tailored to the user environment and daily activities. In this article, we describe the approach developed within the UPCASE project, which makes use of sensors available in the mobile device as well as sensors externally connected via Bluetooth to provide user contexts. We describe the system architecture from sensor data acquisition to feature extraction, context inference and the publication of context information in web-centered servers that support well-known social networking services. In the current prototype, context inference is based on decision trees to learn and to identify contexts dynamically at run-time, but the middleware allows the integration of different inference engines if necessary. Experimental results in a real-world setting suggest that the proposed solution is a promising approach to provide user context to local mobile applications as well as to network-level applications such as social networking services.     

Modeling and generating context-aware agent-based applications with amended colored Petri nets

Context-awareness is become more crucial in mobile distributed computing systems. However, sophisticated modeling methods to analyze context-aware systems are still very few. Among those, the Colored Petri Net (CPN) is promising because it is proven to be useful for modeling system dynamics and concurrency control in more efficient ways. However, to support managing multiple configurations of components of context-aware applications, some features need to be added to specialize the CPNs. To address these challenges, our research has two idea: (a) to decompose a system into several meaningful subsystems, each of which we will call a pattern, and (b) to separate context from the patterns to realize context-pattern independence. Hence, we propose a modeling methodology to represent and analyze a context-aware agent-based system, which tends to be highly complex. We introduce CPNs as a method of capturing the dynamics of this contextual change. We define CPNs and a way to apply them in context-aware agent-based systems. We also describe a prototype system that we have developed called CPN Generator, which translates CPN specification into Java programs.     

ActiveCampus: experiments in community-oriented ubiquitous computing

The continuing proliferation of handheld computing devices offers a new platform for mobile computing applications that could enrich our experience of the world around us. Yet many questions about realizing this vision remain open. We have been investigating these questions at the University of California, San Diego, through the ActiveCampus Project. ActiveCampus explores technologies that can enrich the learning community in the midst of these changes. It explores wireless context-aware computing as a means to enhance the "learning community" experience of a large urban university. We have tested two applications: ActiveClass supports classroom activities, such as asking questions during a lecture, and ActiveCampus Explorer supports context-aware activities, such as instant messaging and location-aware maps annotated with dynamic hyperlinked information.     

Context-aware trails [mobile computing]

The emergence of converged mobile devices with a wide range of computing, communications, entertainment, and sensing capabilities represents a major step in the evolution of wireless computing. Such devices increasingly shift the decision-making power from the user to the machine, which has the capacity to be better informed about the current environment and can respond more quickly. A trail is a collection of locations, together with associated information about these locations and a recommended order for visiting them. Mobile, context-aware trails-based applications range from single-user systems that focus on individual daily activities to multimedia groupware that supports a wide collection of user requirements. The trails metaphor makes it possible to explore adaptive characteristics common to all mobile, context-aware applications. Adaptation in this context involves altering the set of interest points on a trail and their visiting order with timeliness, accuracy, and relevance while remaining in tune with user expectations.     

支持感知上下文网络操作平台中间件的研究

普适计算的出现将大大改变人类与各种设备交互的方式。支持感知上下文计算的网络操作平台是普适计算环境下重要的应用支撑平台,为基于传感器网络的应用提供操作服务。操作平台以中间件为核心,采用XMLWebServices技术。文章以满足包括智能家居普适上下文应用需求的网络操作平台为基础,介绍该网络操作平台的机制、层次结构和数据模型的研究,并实现了基于该平台模型的XMLWebServices中间件应用方案。     

MCSM:一种基于移动设备的上下文感知中间件

提出一种针对移动设备的上下文感知中间件MCSM(Mobile Context Sensing Middleware).MCSM可以动态地感知当前移动设备的内外部计算环境及用户活动等上下文信息,并以统一的接口将感知到的上下文数据提供给上层应用程序.为了克服外部传感器数据的高异构性,MCSM采用了一种基于XML的上下文数据描述语言CDDL.基于MCSM的原型系统表明,MCSM具有良好的运行效率和可扩展性,并可显著提高上下文应用程序的开发效率.     

Integrated Development of Context-Aware Applications in Smart Spaces

When designing context-aware applications for smart spaces, developers must provide interface specifications for perceptual components, which often come from multiple vendors. The authors outline a set of structuring principles that leverage such specifications. IBM has introduced two tools that facilitate the development of smart space applications. Chilix is a middleware library for bridging disaggregated systems, and SitCom is an integrated development environment enabling context modeling, and simulation and lifecycle management of perceptual components. Chilix provides an attractive lightweight alternative to legacy middleware for distributed computing. SitCom supports perceptual component developers, service developers and context-modeling experts across the development life cycle.     

An adaptive middleware framework for context-aware applications

We describe a middleware framework for the adaptive delivery of context information to context-aware applications. The framework abstracts the applications from the sensors that provide context. Further applications define utility functions on the quality of context attributes that describe the context providers. Then, given multiple alternatives for providing the same type of context, the middleware applies the utility function to each alternative and choose the one with maximum utility. By allowing applications to delegate the selection of context source to the middleware, our middleware can implement autonomic properties, such as self-configuration when new context providers appear and resilience to failures of context providers.

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