基于上下文感知和RFID的智能交互系统

上下文感知是在移动计算环境中实现人机自然交互的关键,该文分析在信息空间和物理空间融合环境中,上下文应具有的意义、特征和作用.结合RFID技术的特点和发展趋势,提出通过基于RFID与移动计算获取上下文以进行智能交互的思想.采用被动式RFID标签跟踪并存储上下文数据,以蓝牙作为无线交互信道,结合移动终端PDA实现嵌入式系统,通过实验给出应用效果.该原形系统在可穿戴计算、医疗看护、残障协助和路标导航等方面具有实验推广价值.     

基于无线局域网的室内临近位置检测代理实现

传统基于网络的位置服务系统主要是为远程用户提供查询移动对象位置的信息服务。而现有基于移动终端的位置感知服务不能满足位置上下文应用的要求．为了达到系统自动自发的上下文交互目的。需要在应用中定义一个位置检测代理来捕获移动设备的位置变化事件．生成有效的上下文信息．本文使用简单贝叶斯分类算法实现了基于无线局域网的临近位置检测代理．在室内环境中进行实验表明。该方法可根据实际需要调整位置检测的范围与准确度。具有可行性与灵活性．     

基于移动代理的上下文感知系统研究

上下文表是用上下文信息描述实体状态,原子上下文感知反应则说明了系统根据当前上下文和历史上下文做出合适的响应.基于以上两个概念设计了上下文感知移动代理、系统代理和上下文感知移动代理服务环境,目的是解决普适计算系统需要自动适应用户行为及环境变化的问题.首先使用历史上下文与当前上下文提取上下文表达式,根据该表达式在上下文反应容器中匹配对应的操作,然后由系统代理执行该操作,为用户提供任务相关的服务或者信息.其次根据原子上下文感知提出若干实例,并由上下文感知演算验证,同时指出上下文感知演算的不足.最后,用染色Petri网对一个实例场景仿真,证明了系统的可行性.     

基于上下文感知的智能交互系统模型

上下文感知是提高人机交互智能性的重要途径,上下文信息能否在计算过程中真正发挥其作用主要取决于两个方面：一是从交互环境中提取和形成上下文;二是协调控制各种上下文与高层应用之间的通信．文中围绕这两个问题展开讨论,提出了一种上下文感知和调度的策略,并建立了一个基于上下文感知的智能交互系统结构模型．介绍了按照所述策略和模型构建的实例系统,初步证明了其合理性和有效性．     

基于共享空间的移动Agent交互

在移动agent应用环境中,agent并不是孤立地完成任务,它需要经常与其它agent交互并不断地与环境交互。而基于TupleSpace的交互模型已经被证明是最适合于移动agent环境的。该文将基于TupleSpace的交互模型进行智能性扩展,使其不仅具有反应力而且具有推理和学习能力,并将该模型作为移动agent系统中的交互媒体,支持移动agent之间、agent与系统资源间的交互。实际上,该模型松散耦合到移动agent环境,因而不仅支持交互,它还支持任何异质环境中(包括移动agent系统)的安全问题、效率问题及灵活性问题的解决。     

基于上下文感知计算的移动中间件自适应模式的构建

随着科技的发展,各种智能移动终端已普及到人们生活中,基于上下文感知计算的移动应用已越来越得到人们的关注。然而受现实环境中地理条件的多样性、网络的不稳定性以及用户数量的突变性等因素的影响,现有移动中间件技术已无法满足现实的多样性需要。为此,提出了一种基于上下文感知计算的移动中间件自适应模式,实现移动终端自适应感知上下文、自主存储、推理与分析,降低用户参与度,提高系统自主交互的能力。     

PMIPv6接入方式的实现与对比

代理移动IPv6协议能够在移动主机不参与信令交互的基础上对IPv6主机进行移动管理,这是通过扩展在网络节点和家乡代理之间交互的移动IPv6信令消息格式实现的。代理移动IPv6不需要移动主机与家乡代理进行信令交互。网络中的代理移动实体将代替移动主机与家乡代理进行信令交互并对移动主机进行管理。提出并分析了移动主机接入代理移动IPv6域内的三种方案,分别是二层接入,三层Router Solicitation接入,通用移动管理协议（GMMP）,并对它们进行了比较,即二层接入速度更快,RS接入具有普适性,GMMP接入则更符合标准化。     

基于JADE的企业商务智能服务代理平台

为解决电子商务平台在异构和分布环境下计算实体的协作和协调、快速有效的信息收集及平台的智能化等问题,提出基于移动Agent在JADE上的企业商务智能服务代理平台体系结构模型和实现方法,给出基于多移动Agent的商务服务竞标算法流程和服务实体的行为交互过程,结合实际的应用验证,表明该服务代理平台系统在实际应用中的可行性与有效性。     

手持移动计算中的人机交互技术研究

叙述了在手持移动计算设备上的基于上下文感知的多通道交互模型、多通道汉字输入、移动计算中的小屏幕网络浏览策略等方面的研究成果。实现了一个智能导游系统TGH,对这些模型和方法进行了应用和测试。最后总结了手持移动计算中人机交互技术研究的一些结论。     

消息分发系统中的元组空间分解算法研究

为解决分布式环境下消息分发系统中的按需通信,在对Gelemter元组空间模型进行改进的基础上,对消息分发系统中的元组空间通信进行了结构设计,定义了元组空间的特征模型,并基于局部性原理提出一种元组空间通信的空间分解算法.该算法依据在实际通信中不同元组不同元素的匹配频度的差异,将元组空间分解为依赖特征空间、特征元组和特征元素之间抽象关系的一组缓冲子空间,通信进程在进行匹配操作时可直接从缓冲子空间中获取匹配元组,从而降低通信的计算成本.     

SecSpaces: a Data-driven Coordination Model for Environments Open to Untrusted Agent

In this paper we initiate an investigation about security problems which occur when exploiting a Linda-like data driven coordination model in an open environment. In this scenario, there is no guarantee that all the agents accessing the shared tuple space are trusted. Starting from the analysis of the few proposals already available in the literature, we present a novel coordination model which provides mechanisms to manage tuple access control. The first mechanism supports logical partitions of the shared repository: in this way we can restrict the access to tuples inside a partition, simply by limiting the access to the partition itself. The second mechanism consists of adding to the tuples some extra information which exploit asymmetric cryptography in order, e.g., to authenticate the producer of a tuple or to identify its reader/consumer. Finally, we support the possibility to define access control policies based on the kind of operations an agent performs on a tuple, thus discriminating between (destructive) input and (non-destructive) read operations.     

An architecture for tuple‐based coordination of multi‐agent systems

Multi‐agent system development calls for powerful and expressive coordination models and languages, as well as for an effective coordination technology. A good deal of the current research effort focuses on tuple‐based coordination, exploiting its well‐known advantages, such as agent uncoupling and associative access to information, and addressing its limitations in terms of flexibility and control capabilities. In particular, the behaviour of a Linda‐like tuple space is fixed once and for all by the coordination model, and cannot be tailored to the specific application needs. Tuple centres are tuple spaces whose behaviour can be programmed by defining transactional reactions to the basic communication events, allowing coordination laws to be explicitly defined and embedded into the coordination medium. This paper presents the architecture of a run‐time system for tuple‐based coordination, where tuple centres work as an extensible kernel, around which multi‐agent systems can be designed and deployed. After sketching the implementation, the paper shows the advantages that can be achieved from both the design and the performance viewpoints. Copyright © 1999 John Wiley & Sons, Ltd.     

WCL: A co-ordination language for geographically distributed agents

In this paper a tuple space based co-ordination language, and a run-time system which supports it, is described. The co-ordination language is called WCL, and it is designed to support agent co-ordination over the Internet between agents which are geographically distributed. WCL uses tuple spaces as used in Linda. WCL provides a richer set of primitives than traditional tuple space based systems, and provides asynchronous and synchronous tuple space access, bulk tuple primitives, and streaming primitives which, as a whole, provide a complete framework more suited to co-ordination over the Internet compared with the Linda primitives. The primitives emphasise efficiency and location transparency (of data and agents) and this is exploited in the current run-time system used to support WCL. The run-time system described in this paper is distributed and uses location transparency and dynamic analysis of tuple space usage to migrate tuple spaces around the distributed system. Some initial experimental results are given which demonstrate the performance gains of using the tuple space migration. The paper motivates the inclusion of many of the primitives, and demonstrates how a well designed set of primitives provides performance and efficiency. The JavaSpace primitives are used as an example of how the choice of primitives can detrimentally affect the efficiency of the language, and exclude required co-ordination constructs.     

Agents for information retrieval: Issues of mobility and coordination

This paper focuses on agent-based applications for information retrieval on the Web, by specifically analysing mobility and coordination issues. On the one hand, mobile agents well suit the requirements of information retrieval in the new dynamic scenario derived from the Internet. This is due to their capability of moving to the place where the information is stored – therefore saving bandwidth – and to their robustness in the presence of unreliable connections. On the other hand, the search for information by several mobile active agents calls for suitable models to rule the interactions among agents and between agents and execution environments. The paper surveys different coordination approaches and evaluates their impact in information retrieval applications based on mobile agents. The survey outlines the advantages of uncoupled coordination models and points out the suitability of a coordination model based on reactive and programmable tuple spaces: they may increase the safety and the security of the environment while simplifying the task of programming distributed mobile agent applications.     

A Fault-tolerant model for tuple space coordination in distributed environments

In distributed systems, tuple space is one of the coordination models that significantly maximizes system performance against failure due to its space and time decoupling features. With the growing popularity of distributed computing and increasing complexity in the network, host and link failure occurs frequently, resulting in poor system performance. This article proposes a fault-tolerant model named Tuple Space Replication (TSR) for tuple space coordination in distributed environments. The model introduces a multi-agent system that consists of multiple hosts. Each host in a multi-agent system comprises an agent space with a tuple space for coordination. In this model, we introduce three novel fault-tolerant algorithms for tuple space primitives to provide coordination among hosts with tolerance to multiple links and hosts failure. The first algorithm is given for out() operation to insert tuples in the tuple space. The second algorithm is presented for rdp() operation to read any tuple from the tuple space. The third algorithm is given for inp() operation to delete or withdraw tuples from the tuple space. These algorithms use less number of messages to ensure consistency in the system. The message complexity of the proposed algorithms is analyzed and found O(n) for out(), O(1) for rdp(), and O(n) for inp() operations which is comparable and better than existing works, where n is the number of hosts. The testbed experiment reveals that the proposed TSR model gives performance improvement up to 88%, 70.94%, and 63.80% for out(), rdp(), and inp() operations compared to existing models such as FT-SHE, LBTS, DEPSPACE, and E-DEPSPACE.     

Mobile Agent Coordination for Distributed Network Management

Mobile agents are a promising technology to face the problems raised by the increasing complexity and size of today's networks. In particular, in the area of network management, mobile agents can lead to a fully distributed paradigm to overcome the limits of traditional centralized approaches. A basic requirement for the management of a complex network is the definition of high-level and flexible models to coordinate the accesses to the resources—data and services—provided by the network nodes. On this basis, this paper describes the MARS coordination architecture for mobile agents. MARS is based on the definition of programmable tuple spaces associated with the network nodes: mobile agents can access the local resources and services via the tuple space, thus adopting a standard and high-level interface. The network administrator—via mobile agents—can dynamically program the behavior of the tuple space in reaction to the agents' access to the tuple space, thus leading to a flexible network model. Several examples show the effectiveness of the MARS approach in supporting network management activities.     

Engineering mobile agent applications via context-dependent coordination

The design and development of Internet applications requiring dynamic and possibly mobile access to Internet resources can take advantage of an approach based on autonomous mobile agents. However, mobility introduces peculiar issues related to the modeling and management of the agents' coordination activities. This paper introduces context-dependent coordination as a framework for the design and development of Internet applications based on mobile agents, and shows how it can be supported by a proper coordination infrastructure. Context-dependent coordination is centered on the notion of programmable coordination media, as the software abstraction via which an agent in an Internet site can access to local resources and coordinate with local agents. Programmability stems from the fact that the behavior of the media can be fully configured to influence agents' coordination activities. This enables local administrators to configure coordination media so as to enact site-dependent coordination policies, and mobile agents to configure the accessed coordination media to obtain an application-dependent behavior of the media themselves. Several application examples shows that exploiting context-dependent coordination promotes a clear separation of concerns in design and development, and can make applications more modular and easier to be maintained. The MARS system is assumed as an exemplar coordination infrastructure to clarify the concepts expressed and to show their actual implementation.     

Data Privacy in Tuple Space Based Mobile Agent Systems

More recently, distributed variants of tuple spaces have been proposed to exploit the Linda model for programming distributed applications over wide area networks, possibly exploiting code mobility. However, the flexibility of the shared tuple space model opens possible security holes; it basically provides no access protection to the shared data. In this paper we investigate some possible scenarios where mobile agents can benefit from our cryptographic tuple space based framework, CryptoKlava, and sketch how to possibly implement such agents in order to keep the privacy of items collected by the mobile agent during its itinerary. The functionalities of the framework are general enough to be applied to other Java frameworks using multiple distributed tuples spaces possibly dealing with code mobility.     

MULTI-AGENT INFRASTRUCTURES FOR OBJECTIVE AND SUBJECTIVE COORDINATION

Coordination in multi-agented systems (MAS) can be conceived as either an agent activity (the subjective viewpoint) or an activity over agents (the objective viewpoint). The two viewpoints have generated two diverging and often contrasting lines of research, as well as different and noncompatible technologies, however, their integration is mandatory for modeling and engineering complex MAS. In this paper, we explore the issue of integration at both the model and the technology levels.

First, by taking FIPA agents and coordination artifacts as reference notions for subjective and objective approaches, respectively, we sketch a framework where agent interactions with coordination artifacts are modeled as physical acts, deliberated and executed by agents analogously to communicative actions. Then, we show how the JADE infrastructure for FIPA-compliant agents, and the TuCSoN infrastructure providing agents with coordination artifacts can be integrated at the technology level, allowing JADE agents to access TuCSoN tuple centers through JADE services.     

Coordinating Mobile Agents by the XML-Based Tuple Space

This paper presents Xspace,a programmable coordination paradigm for Internet applications based on mobile agents.The Xspace system fully exploits the advantages of the XML language and Linda-like coordination.It supports XML documents as tuple fields and multiple matching routines implementing different relations among XML documents,including those given by XML query languages,The Xspace uses Java as the implementation language;it is based on object-oriented XMLized tuple spaces to implement a portable and programmable coordination paradigm for mobile agents.The dsign and implementation procedures of Xspace are described in this paper,Experiment and performance evaluation are also made.Finally,some conclusinos and remarks are given.