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。     

Context-aware hybrid reasoning framework for pervasive healthcare

Pervasive computing has emerged as a viable solution capable of providing technology-driven assistive living for elderly. The pervasive healthcare system, Context-Aware Real-time Assistant (CARA), is designed to provide personalized healthcare services for elderly in a timely and appropriate manner by adapting the healthcare technology to fit in with normal activities of the elderly and working practices of the caregivers. The work in this paper introduces a personalized, flexible, and extensible hybrid reasoning framework for CARA system in a smart home environment which provides context-aware sensor data fusion as well as anomaly detection mechanisms that supports activity of daily living analysis and alert generation. We study how the incorporation of rule-based and case-based reasoning enables CARA to become more robust and to adapt to a changing environment by continuously retraining with new cases. Noteworthy about the work is the use of case-based reasoning to detect conditional anomalies for home automation, and the use of hierarchical fuzzy rule-based reasoning to deal with exceptions and to achieve query-sensitive case retrieval and case adaptation. Case study for evaluation of this hybrid reasoning framework is carried out under simulated but realistic smart home scenarios. The results indicate the feasibility of the framework for effective at-home monitoring.     

Context-aware active task discovery for pervasive computing

Task computing is mainly involved with how to interact with equipment and services for users. In such new mode users can only concern with the task need to be completed, without having to consider how to complete it. In recent years, this new mode has been considered the preferred choice under the environment of pervasive computing. Active task discovery is the key to task computing, which depends on context and automatically relates the corresponding services to complete the given operation. In this paper, based on active task computing model we present a new context-aware active task discovery mode and raise a good algorithm for discovering and executing task.     

普适计算中上下文依赖的主动任务发现

任务计算是一种针对用户如何与设备和服务进行交互的新模式,用户可以只关注需要完成的任务,而不必考虑如何去完成。主动任务发现是任务计算的核心,它依赖于上下文,并能自动组合相应的服务完成规定的操作。在构建任务计算模型的基础上,描述了一种基于上下文依赖的主动任务发现模式,分析了主动任务的结构模型,提出了一种发现任务并执行任务的算法,并通过一个智能教室的应用环境说明了该算法的具体应用。     

Web服务组合策略研究及组合决策平台实现

由于关注点的不同和客观环境的多样性,Web服务组合方法的种类纷繁复杂。如何从零碎散乱的不同决策角度出发来构建可行而高效的组合方法,是现阶段Web服务组合研究中亟待解决的关键问题之一。因此,本研究将注意力放在一套可以帮助Web服务组合实践者选择服务组合方法的决策机制上。考虑到层次分析法可以用来帮助解决这个多阶段多标准问题,分析综合了前人的相关研究成果,从而根据层次分析法构建结构树,进而举例详细阐述了如何在多个备选方案中做出最佳选择的Web服务组合决策机制。最后,为帮助Web服务组合实践者理解和使用这套决策机制,也设计并实现了一个决策平台easyWSC,现已开放给相关研究人员和实践者使用、讨论和改进。     

Context-aware service engineering: A survey

Context constitutes an essential part of service behaviour, especially when interaction with end-users is involved. As observed from the literature, context handling in service engineering has been during recent years a field of intense research, which has produced several interesting approaches. In this paper, we present research efforts that attempt mainly to decouple context handling from the service logic. We enumerate all context management categories, but focus on the most appropriate for service engineering, namely source code level, model-driven and message interception, taking also into account the fact that these have not been dealt with in detail in other surveys. A representative example is used to illustrate more precisely how these approaches can be used. Finally, all three categories are compared based on a number of criteria.     

基于抽象服务的密码服务组合模型设计与实现

传统的密码服务与应用系统的紧耦合,不能满足新的业务需求,同时严重制约了密码服务的发展。为了提高密码服务质量和扩展其应用范围,根据密码服务的特点,对其进行抽象归类,构建抽象服务。并在此基础上结合面向服务的体系架构,利用BPEL和Pi演算的转换,设计了可以动态调度和智能优化的密码服务组合模型。该模型不但可以实现业务流程的图形化编排,而且可以对流程进行形式化分析和正确性检测。最后给出了原型系统的设计思想和实现方法。     

一种丢包率比例区分服务及其实现*

摘要：针对区分服务的定量描述和提供问题,基于比例区分模型提出了一种丢包率比例区分的确保服务,并给出了一种基于丢包率测量和动态调节RED队列最大丢包概率因子的实现机制。作为区分服务模型的一种扩充,丢包率比例区分服务有利于运营商制定细致的价格策略,也便于用户平衡价格和性能因素选择合适的服务。     

Context-aware trust negotiation in peer-to-peer service collaborations

Service-oriented architecture (SOA) and Software as a Service (SaaS) are the latest hot topics to software manufacturing and delivering, and attempt to provide a dynamic cross-organisational business integration solution. In a dynamic cross-organisational collaboration environment, services involved in a business process are generally provided by different organisations, and lack supports of common security mechanisms and centralized management middleware. On such occasions, services may have to achieve middleware functionalities and achieve business objectives in a pure peer-to-peer fashion. As the participating services involved in a business process may be selected and combined at run time, a participating service may have to collaborate with multiple participating services which it has no pre-existing knowledge in prior. This introduces some new challenges to traditional trust management mechanisms. Automated Trust Negotiation (ATN) is a practical approach which helps to generate mutual trust relationship for collaborating principals which may have no pre-existing knowledge about each other without in a peer-to-peer way. Because credentials often contain sensitive attributes, ATN defines an iterative and bilateral negotiation process for credentials exchange and specifies security policies that regulate the disclosure of sensitive credentials. Credentials disclosure in the iterative process may follow different orders and combinations, each of which forms a credential chain. It is practically desirable to identify the optimal credential chain that satisfies certain objectives such as minimum release of sensitive information and minimum performance penalty. In this paper we present a heuristic and context-aware algorithm for identifying the optimal chain that uses context-related knowledge to minimize 1) the release of sensitive information including both credentials and policies and 2) the cost of credentials retrieving. Moreover, our solution offers a hierarchical method for protecting sensitive policies and provides a risk-based strategy for handling credential circular dependency. We have implemented the ATN mechanisms based on our algorithm and incorporated them into the CROWN Grid middleware. Experimental results demonstrate their performance-related advantages over other existing solutions.

Context-aware environments: from specification to implementation

Abstract: This paper deals with the problem of implementing a context model for a smart environment. The problem has already been addressed several times using many different data- or problem-driven methods. In order to separate the modelling phase from implementation, we first represent the context model by a network of situations. Then, different implementations can be automatically generated from this context model depending on user needs and underlying perceptual components. Two different implementations are proposed in this paper: a deterministic one based on Petri nets and a probabilistic one based on hidden Markov models. Both implementations are illustrated and applied to real-world problems.     

基于情境感知的智慧矿山服务系统研究

随着矿山信息化技术的快速发展,信息系统的种类和数量日益增多,但其服务对象主要限于管理人员,落后的信息管理模式使得绝大多数一线矿工难以获得及时的信息服务,无法有效预防各类安全隐患,造成信息资源的极大浪费.针对以上问题,结合煤矿自身的行业特点,将情境感知技术引入到智慧矿山的建设中,构建了一个基于情境感知的智慧矿山服务系统,通过情境信息采集、情境信息推理、服务配置模型等关键步骤,能够实时感知井下矿工的情境需求,提供更加智能化的业务服务或服务组合,并能实现对煤矿遗留信息系统的充分利用以及更全面的互联互通.最后,通过仿真环境下的测试说明了构建该服务系统的过程以及实施情境感知服务的效果,并对可能存在的各种潜在问题进行了讨论.     

Context-aware QoS prediction for web service recommendation and selection

QoS prediction is one of the key problems in Web service recommendation and selection. The context information is a dominant factor affecting QoS, but is ignored by most of existing works. In this paper, we employ the context information, from both the user side and service side, to achieve superior QoS prediction accuracy. We propose two novel prediction models, which are capable of using the context information of users and services respectively. In the user side, we use the geographical information as the user context, and identify similar neighbors for each user based on the similarity of their context. We study the mapping relationship between the similarity value and the geographical distance. In the service side, we use the affiliation information as the service context, including the company affiliation and country affiliation. In the two models, the prediction value is learned by the QoS records of a user (or a service) and the neighbors. Also, we propose an ensemble model to combine the results of the two models. We conduct comprehensive experiments in two real-world datasets, and the experimental results demonstrate the effectiveness of our models.     

基于Parlay的状态感知通信业务技术及实现

提出了综合上下文感知技术和融合网络通信技术的下一代网络新业务——状态感知通信业务。讨论了基于遍布计算的网络层状态感知技术以及基于Parlay API的应用层状态感知技术,综合这两层状态感知技术提出了状态感知通信系统的结构和控制流程,并给出了应用示例。     

基于BPMN的服务组合执行引擎的研究与实现*

业务模型和执行模型的一致性是当前服务组合研究的一个难点和热点。目前普遍采用模型转换的方式将业务模型映射为可执行模型,但由于两种模型语言的语义和语法不一致,导致了模型转换存在语义失配等缺陷。针对该问题,提出了一种基于业务流程建模标注的Web服务组合执行方案,设计了BPMN模型的解释执行算法,给出了执行引擎的原型系统,并通过具体案例验证了方案的有效性。     

Aspect-oriented design and implementation of context-aware pervasive applications

Pervasive applications must be aware of the contexts where they are executed. These contexts may vary greatly and change quickly. Two main problems are associated with this issue: (1) context-awareness is a crosscutting concern that cannot be well-encapsulated in a single module using traditional technologies, thus hindering software maintenance and reusability; and (2) reasoning about application design correctness can be complex due to the number and diversity of potential contexts where a pervasive application could be executed. In order to overcome these problems, we present a process for the design and implementation of context-aware pervasive applications that uses aspect-orientation and executable modelling in order to overcome these shortcomings. Aspect-oriented techniques contribute to the encapsulation of crosscutting concerns, such as context-awareness, into well-localized modules. Executable modelling helps engineers to reason about application design by executing the design models in different contexts and situations. Pervasive applications are modelled using the aspect-oriented executable modelling UML 2.0 profile, executed at the modelling level for testing purposes, and then mapped into an aspect-oriented middleware platform for pervasive applications. This process is illustrated using a location-aware intelligent transportation system consisting of a set of cooperating sentient vehicles. This work has been supported by the Spanish Ministerio de Ciencia y Tecnologa (MCYT) Project TIN2005-09405-C02-01 and the European Commission Grant IST-2-004349-NOE AOSD-Europe and the European Commission STREP Project AMPLE IST-033710.     

Context-aware intelligent service system for coal mine industry

In coal mine industry, the context-aware intelligent service system can be used to provide the most appropriate information services to miners according to their real-time situation. As a result, the information resources can be taken full advantage of so as to help miners to improve their safety condition, which are not just accessible to the management staff. However, there is not a detailed discussion or an in-depth research on the implementation of service system at present. In order to bridge the gap between the theory and the practice in the field, three critical problems need to be solved: (1) How to model the served miners’ context? (2) How to provide the information services to meet miners’ customized demands? (3) How to verify the availability of service invocation? According to the characteristics and practical needs of coal mine, this paper first proposes the Coal Mine Semantic Sensor Network Ontology (CMSSN) to build miner's context model, which can facilitate reusing the context resources in different coal mines. Then, the configuration model connecting context information and business services is constructed to realize the customized service invocation. Thirdly, the method of computational experiment is proposed to verify the availability and validity of service system, i.e. whether the service system can provide the suitable service on time in various virtual accident experiments. A case study is given to explain how to implement the computational experiment on a virtual coal mine simulation platform. Finally, the potential problems in realizing the system are discussed, which will be our research focus in future.     

A conceptual model of service customization and its implementation

With the development of Internet and next generation networks in telecommunications, more and more new services are required to be introduced into networks. Introducing new services into traditional network is always associated with standardizing new protocols. The progress of protocol standardization usually takes several years, which cannot meet the increasing demands of the applications in Internet and next generation networks. Service customization in network systems may be one possible solution to cope with this problem. Based on the principle that network service is provided by interactions among protocol entities, this paper proposes a conceptual model of service customization (SECUM) by separating the service logic from protocol interactive logic within existing network architecture. The theory of Communicating Sequential Processes (CSP) is used to formalize the SECUM in order to locate exactly the service logic and to define precisely the SECUM. For validating the SECUM‘s usability in practical network systems, this paper also proposes an implementation model for SECUM: a component-based protocol implementation model (CPIM). CPIM discomposes protocol entity into application component, service component, message component and communication component. Service component associates application component with message component. Users or network managers can customize network services by configuring service component. The paper shows respectively the applications of SECUM and CPIM by proposing a customizable IP service model based on SECUM and describing an implementation of Session Initiation Protocol (SIP) based on CPIM. Compared with the existing service-customization techniques, SECUM is a service customization model internal to network system and may provide more powerful capabilities of service customization.     

Spatial-aware service management in a pervasive environment

We can perceive the advent of Internet of Things enriched pervasive environments attributed to the fast emerging of embedded and interconnected intelligent devices and sensors. However, most of current pervasive systems are still being developed based on the so-called the system is the application philosophy, causing the developers to take care of all technical details from the ground up. There is relatively little research focuses on building higher-level abstractions so that the burdens of developers can be relieved. The abstraction of a “place,” also known as an “Ambient,” is an essential context information when implementing a pervasive system. The quality of the results of a service composition can be improved if the concept of Ambient is taken into account. This paper aims to investigate the use of Ambient in the pervasive system systematically. We propose several new spatial abstractions and a spatial-aware service management scheme for the Ambient on top of a robust service management protocol. Formal verification, complexity analysis, and experiments are performed to verify the robustness, efficiency, and performance of the proposed approach, respectively.     

Context-driven personalized service discovery in pervasive environments

Pervasive environments are characterized by a large number of embedded devices offering their services to the user. Which of the available services are of most interest to the user considerably depends on the user’s current context. User context is often rich and very dynamic; making an explicit, user-driven discovery of services impractical. Users in such environments would instead like to be continuously informed about services relevant to them. Implicit discovery requests triggered by changes in the context are therefore prevalent. This paper proposes a proactive service discovery approach for pervasive environments addressing these implicit requests. Services and user preferences are described by a formal context model called Hyperspace Analogue to Context, which effectively captures the dynamics of context and the relationship between services and context. Based on the model, we propose a set of algorithms that can continuously present the most relevant services to the user in response to changes of context, services or user preferences. Numeric coding methods are applied to improve the algorithms’ performance. The algorithms are grounded in a context-driven service discovery system that automatically reacts to changes in the environment. New context sources and services can be dynamically integrated into the system. A client for smart phones continuously informs users about the discovery results. Experiments show, that the system can efficiently provide the user with continuous, up-to-date information about the most useful services in real time.