STRATEGIES FOR COOPERATION EMERGENCE IN DISTRIBUTED SERVICE DISCOVERY

In distributed environments where entities only have a partial view of the system, cooperation is a key issue. In the case of decentralized service discovery in open agent societies, agents only know about the services they provide and who their direct neighbors are. Therefore, they need the cooperation of their neighbors in order to locate the required services. However, cooperation is not always present in open systems. Noncooperative agents pursuing their own goals could refuse to forward queries from other agents to avoid the cost of this action; therefore, the efficiency of the decentralized service discovery could be seriously damaged. In this article, we propose the combination of incentives and local structural changes in order to promote cooperation in the service discovery process. The results show that, even in scenarios where the predominant behavior is not collaborative, cooperation emerges.     

一种基于本体和Agent的网格服务发现机制

在动态的网格计算环境中分布着大量不同类型的网格服务。快速、准确地进行网格服务发现是影响网格计算性能的关键因素。本文提出了基于本体和Agent的网格服务发现机制,它具有良好的扩展性和完备性。该模型采用Agent代理技术进行服务搜索,不同的代理能够提供不同虚拟组织的本体知识库;利用本体论语义进行服务的匹配,从而实现智能化的服务发现。     

Semantic Web service discovery: state-of-the-art and research challenges

Ubiquitous computing paradigms involving social agents require principled selection of services, context-aware analysis, and satisfaction of requests, as well as dynamic interaction and negotiation with other agents. Synergies between semantic technologies and service discovery facilitate rich and formal representations of services and agent interactions as well as specialization and generalization of service needs. In this paper, we provide an extensive review of semantic Web service discovery, highlighting the state-of-the-art approaches, the key semantic formalisms employed, as well as benchmarks and testbeds for performance evaluation. Defining a generic framework for semantic service discovery, we describe the key tasks and criteria involved in agent-based computing. A detailed comparison of the popular discovery systems is performed with a discussion on trade-offs between existing approaches. We conclude by pointing out important research challenges to be addressed for next-generation service discovery by dynamic multi-agent systems in complex environments.     

Composing web services enacted by autonomous agents through agent-centric contract net protocol

ContextAgents are considered as one of the fundamental technologies underlying open and dynamic systems that are largely enabled by the semantic web and web services. Recently, there is a trend to introduce the notion of autonomy empowered by agents into web services. However, it has been argued that the characteristics of autonomy will make agents become available intermittently and behave variedly over time, which therefore increase the complexity on devising mechanisms for composing services enacted by autonomous agents.ObjectiveIn this work, we propose an extension to Contract Net protocol, called Agent-centric Contract Net Protocol (ACNP), as a negotiation mechanism with three key features for composing web services enacted by autonomous agents.Method(1) A matchmaking mechanism embedded in a middle agent (as a service matchmaker) for discovering web services that are available intermittently is presented based on the concept of agent roles; (2) A selection algorithm based on risk-enabled reputation model (REAL) embedded in a manager agent (as a service composer) is introduced to serve a basis for selecting web services with variant performance; and (3) A negotiation mechanism between a manager agent and contractor agents (as atomic services) is devised and enables both a service composer and the atomic services to request, refuse or agree on adapting changes of services.ResultsThe problem of assembling a computer is discussed in this paper.ConclusionIt is increasingly recognised that web services would become more autonomous by introducing diverse agent technologies to better constitute more complex systems in open and dynamic environments. As web service technologies are best exploited by composite services, it is imperative to devise mechanisms for composing services of autonomy.     

A P2P strategy for QoS discovery and SLA negotiation in Grid environment

In recent years, Grid systems and Peer to Peer networks are the most commonly-used solutions to achieve the same goal: the sharing of resources and services in heterogeneous, dynamic, distributed environments. Many studies have proposed hybrid approaches that try to conjugate the advantages of the two models. This paper proposes an architecture that integrates the P2P interaction model in Grid environments, so as to build an open cooperative model wherein Grid entities are composed in a decentralized way. In particular, this paper focuses on a QoS aware discovery algorithm for P2P Grid systems, analyzing protocol and explaining techniques used to improve its performance.     

Economics‐inspired decentralized control approach for adaptive grid services and applications

Grid technologies facilitate innovative applications among dynamic virtual organizations, while the ability to deploy, manage, and properly remain functioning via traditional approaches has been exceeded by the complexity of the next generation of grid systems. An important method for addressing this challenge may require nature‐inspired computing paradigms. This technique will entail construction of a bottom‐up multiagent system; however, the appropriate implementation mechanism is under consideration in order for the autonomous and distributed agents to emerge as a controlled grid service or application. A credit card management service in economic interactions is considered in this article for a decentralized control approach. This consideration is based on a preliminarily developed ecological network‐based grid middleware that has features desired for the next generation grid systems. The control scheme, design, and implementation of the credit card management service are presented in detail. The simulation results show that (1) agents are accountable for their activities such as behavior invocation, service provision, and resource utilization and (2) generated services or applications adapt well to dynamically changing environments such as agent amounts as well as partial failure of agents. The approach presented herein is beneficial for building autonomous and adaptive grid applications and services. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1269–1288, 2006.     

A biologically inspired multimedia content repurposing system in heterogeneous environments

The application of biologically inspired algorithms to multimedia repurposing systems in heterogeneous network environments is gaining importance due to its ability to adapt and customize multimedia content to frequently changing network environments. This paper presents a biologically inspired proxy-based multimedia content adaptation system, which is used to repurpose multimedia content dynamically for the transmission over heterogeneous networks and end devices. We use a series of repurposing proxies’ services in a chain fashion between the sender and multiple end devices. In order to find the appropriate chain of repurposing services that satisfy the Quality of Experience (QoE) requirements, the proposed service selection algorithm uses the ant colony metaphor. During the communication session, the algorithm uses biological foraging behavior inspired from ant agents to find optimal service paths between the media sender and the destination. Experimental results demonstrate that the proposed algorithm provides significant performance gain over traditional, state of the art selection algorithms and saves the average delay.     

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     

Decentralized service discovery and selection in Internet of Things applications based on artificial potential fields

The Internet of Things (IoT) vision involves a future Internet integrated with real-world objects that can commonly offer their functionality trough services. In such pervasive environments of IoT networks, locating and invoking suitable services is quite challenging and traditional service discovery and selection approaches have been proven inadequate. In this paper, taking inspiration from natural metaphors, a decentralized service discovery and selection model is proposed. The model is based on artificial potential fields (APFs) which are formed upon each user service request and become active at points where services can be provided. Such points are termed as service provision nodes (SPNs). The strength of each APF depends on the percentage of requested services that can be provided by the respective SPN, as well as on SPN service load and availability with the aim to balance service load among SPNs. Service discovery and selection is then driven by artificial forces applied among user service requests and SPNs. Simulation results indicate that the proposed approach maintains satisfactory performance and scalability as the number of SPNs in an IoT network increase and efficient load balancing of the requested services among the SPNs in comparison with other approaches.     

一种基于多Agent系统的云服务自组织管理方法

在开放动态的互联网环境下的云服务呈现出发散、动态演化、异构等特征,为了适应多样的应用需求以及持续变化的云环境,云需要以灵活、适应的方法来有效地管理和提供云服务.针对这一需求,提出了一种云服务自组织管理方法,该方法利用agent的环境感知和自主行为决策的能力,依据它的职责实现对云服务的自主管理,并通过agent间的交互以自组织的方式实现对服务资源的有效管理,进而适应云环境和应用需求的变化;提出了支持上述方法和机制的实现技术,包括云服务自组织管理的核心机制和实现框架、云服务汇聚和提供的运行机制及相关实现算法.利用支持语义Web服务发现匹配的公共测试数据设计并完成了两组验证实验,实验结果表明:所提出的方法可以在持续变化的云环境下有效地管理和提供云服务,进而满足动态多样化的应用需求.     

Applying intelligent agents and semantic web services in eGovernment environments

The increasing volume of eGovernment‐related services is demanding new approaches for service integration and interoperability in this domain. Semantic web (SW) technologies and applications can leverage the potential of eGovernment service integration and discovery, thus tackling the problems of semantic heterogeneity characterizing eGovernment information sources and the different levels of interoperability. eGovernment services will therefore be semantically described in the foreseeable future. In an environment with semantically annotated services, software agents are essential as the entities responsible for exploiting the semantic content in order to automate some tasks, and so enhance the user's experience. In this paper, we present a framework that provides a seamless integration of semantic web services and intelligent agents technologies by making use of ontologies to facilitate their interoperation. The proposed framework can assist in the development of powerful and flexible distributed systems in complex, dynamic, heterogeneous, unpredictable and open environments. Our approach is backed up by a proof‐of‐concept implementation, where the breakthrough of integrating disparate eGovernment services has been tested.     

A SUPER‐AGENT‐BASED FRAMEWORK FOR REPUTATION MANAGEMENT AND COMMUNITY FORMATION IN DECENTRALIZED SYSTEMS

In this article, we propose a novel super‐agent‐based framework for reputation management and community formation in decentralized systems. We describe this framework in the context of Web service selection where agents with more capabilities act as super‐agents. These super‐agents serve as reputation managers to maintain reputation information of services and share the information with other consumer agents that have fewer capabilities than the super‐agents. In addition, super‐agents can maintain communities and build community‐based reputation for a service based on the opinions from all community members that have similar interests and judgement criteria as the super‐agents or the other community members. A practical reward mechanism is also introduced to create incentives for super‐agents to contribute their resources (to maintain reputation and form communities) and provide truthful reputation information. Experimental results obtained through simulation confirm that our approach achieves better effectiveness and scalability compared to the systems that do not use super‐agents and that do not form communities.     

CoABS Grid Scalability Experiments

The CoABS Grid is middleware that integrates heterogeneous agent-based, object-based, and legacy systems. It includes a method-based application programming interface to register agents, advertise agent capabilities, discover agents based on their capabilities, and send messages between agents. Agent registration and discovery are reliant on one or more lookup services. The experiments discussed in this paper investigate how timing of sequential agent registration and lookup varies as the total number of registered agents increases. No degradation in performance was observed in experiments with up to 10,000 agents for lookup. Minimal degradation in registration time was observed as the number of registered agents increased. Further experiments are planned.     

基于信誉的语义Web服务发现

服务发现在语义Web领域是一个挑战性问题.一个关键问题是发现满足用户功能需求的最佳服务.同样重要的是,电子商务应用还要求发现满足QoS需求的最佳服务.由此提出一个基于信誉管理的分布式服务选择框架.它主要有以下特点：用一个结构化的覆盖网络作为分布式服务存储系统来提高系统的有效性和可扩展性; 提出一个QoS感知的语义Web服务发现方法,并给出基于用户反馈的分布式信誉度评估算法.最后用一个例子示范算法如何解决实际问题.     

A secure information service for monitoring large scale grids

The Grid Information Service (GIS) is a core component in the Grid software infrastructure. It provides diverse information to users or other service components in Grid environments. In this paper, we propose a scalable GIS architecture for information management in a large scale Grid Virtual Organization (VO). This architecture consists of the VO layer, site layer and resource layer: at the resource layer, information agents and pluggable information sensors are deployed on each resource monitored. This information agent and sensor approach provides a flexible framework that enables specific information to be captured; at the site layer, a site information service component with caching capability aggregates and maintains up-to-date information of all the resources monitored within an administrative domain; at the VO layer, a peer-to-peer approach is used to build a virtual network of site information services for information discovery and query in a large scale Grid VO. This decentralized approach makes information management scalable and robust. Furthermore, we propose a security framework for the GIS, which provide security policies for authentication and authorization control of the GIS at both the site and the VO layers. Our GIS has been implemented based on the Globus Toolkit 4 as Web services compliant to Web Services Resource Framework (WSRF) specifications. The experimental results show that the GIS presents satisfactory scalability in handling information for large scale Grids.     

Integrate software agents and CORBA in computational grid

This paper presents an Agent-based Computational Grid (ACG), which applies the concept of CORBA and agent to computational grid. The ACG system is used to implement a uniform higher level management of the computing resources and services on the Grid, and provide users with a consistent and transparent interface for accessing such services. In ACG grid, grid services are implemented by CORBA or by grid agent. Grid agents and CORBA objects will interact with each other to achieve user's service request. Our solution is the creation of a bridge between the CORBA and grid agents. The solution provides with the opportunity of considering an agent as a CORBA service and accessing CORBA services even from a grid agent. Thus, in AGC grid, existing legacy systems can be easily exploited as grid services. In this paper, firstly, the features of ACG grid are described, and then the design and implementation are given. Finally, some conclusions are given.     

Autonomous Adaptive Agents for Single Seller Sealed Bid Auctions

In developing open, heterogeneous and distributed multi-agent systems researchers often face a problem of facilitating negotiation and bargaining amongst agents. It is increasingly common to use auction mechanisms for negotiation in multi-agent systems. The choice of auction mechanism and the bidding strategy of an agent are of central importance to the success of the agent model. Our aim is to determine the best agent learning algorithm for bidding in a variety of single seller auction structures in both static environments where a known optimal strategy exists and in complex environments where the optimal strategy may be constantly changing. In this paper we present a model of single seller auctions and describe three adaptive agent algorithms to learn strategies through repeated competition. We experiment in a range of auction environments of increasing complexity to determine how well each agent performs, in relation to an optimal strategy in cases where one can be deduced, or in relation to each other in other cases. We find that, with a uniform value distribution, a purely reactive agent based on Cliff’s ZIP algorithm for continuous double auctions (CDA) performs well, although is outperformed in some cases by a memory based agent based on the Gjerstad Dickhaut agent for CDA.     

基于CORBA的分布式Agent通信构架

随着Internet的不断发展,传统的搜索引擎在信息获取上显露出明显的不足。Agent技术的出现使得个性化的主动信息服务成为可能,但是单个Agent的能力有限,因此需要在Agent之间进行通信与交流,实现社会过滤以提高信息服务的质量,为了解决Agent的运行平台和底层通信机制的异构性问题,提出了基于公用对象请求代理体系结构CORBA的分布式Agent通信构架－－CADA.Agent获取用户的信息需求并用KQML进行描述,它通过通信器与其他Agent进行信息交流,通信器对接收到的服务请求进行过滤,将其转发到能够提供该服务的Agent,最后把处理结果返回给客户端．CADA屏蔽了运行平台和底层通信机制,能够有效地解决分布式Agent的通信问题。     

一种考虑服务质量的服务发现机制

服务发现是服务框架中联系消费者和提供者的重要环节。提出了一种考虑服务质量的服务发现机制（QSCD)。QSCD根据消费者的消费历史,考虑了消费者对服务质量的要求,在消费者本地建立一个服务发现机构。并在QSCD引入服务预约和服务社区等概念,对该机制进行了扩展。它作为对已有服务发现机制的补充,可提高发现的速度。     

A new method for the informed discovery of resources in the grid system using particle swarm optimization algorithm (RDT_PSO)

Nowadays, there has been a growing interest in investigating and improving the methods used for resource discovery and access in grid systems, the reason could be the important role of resource exploration methods in determining the quality and performance of grid systems. With the development of grid environments and the increase in the number of resources and geographical distribution, finding new algorithms to discover the required resources at a minimized resource discovery timespan is considered an important task. In this study, by using the intelligent resource discovery model as well as the decentralized method, it is shown that the optimal resource may be searched for reservation and allocation with the least number of visited nodes and the minimum time possible. In order to find the quickest path, the proposed algorithm was optimized using the particle swarm optimization algorithm; then it was compared to the BITMAP and Footprint Resource Discovery Tree, which are among the hierarchical methods of resource discovery. According to the results, the number of visited nodes in the proposed method was found be lower than those of other methods.