一种改进的动态合同网协议

对动态合同网协议进行了改进,提出了一种改进的动态合同网协议。管理者进行决策时不仅考虑信任度还综合相应的承包商代价。此外,给出了此动态合同网协议的算法。经过在REPAST平台上的实验,证明了IDCNP协议在运算时间及通信量方面的优越性。     

一种具有容错能力的动态合同网*

为了适应更为复杂的系统环境应用,提出一种具有容错功能的动态合同网算法。该算法引入任务时限概念以监测系统中的承包商主体,发现故障承包商主体以后,通过撤销承包合同和重新发布任务来保证系统的任务完成率,并重新定义信任度的更新准则;管理器能避免将任务分发给故障承包商,有效减少出错任务的数目,并将故障承包商无法完成的任务二次转发,具有容错能力。实验结果证明了算法的有效性。     

Performance enhancement of a contract net protocol based system through instance-based learning.

The contract net protocol (CNP) is a widely used coordination mechanism in multiagent systems. It has a lot of communication overhead due to the broadcast of the task announcements. The performance of the CNP degrades drastically when the number of communicating agents and the number of tasks announced increases. Hence, it has problems of scalability. In order to overcome this limitation, an instance-based learning (IBL) mechanism is designed that uses previously stored instances in order to select a target agent. This avoids the expensive bidding process. The scheme is implemented in a simulated distributed hospital system where the CNP is used for resource sharing across hospitals. Experimental results demonstrate that with the incorporation of the IBL, the system performance improves significantly. The system is better scalable with respect to the number of tasks.     

基于面向对象Petri网的动态合同网协议通用模型

传统的合同网协议模型通过管理Agent和承包商Agent之间招投标进行交互和协商以共同完成目标任务。但传统合同网协议模型也存在一些如协作过程中通信量大、通用性不强等问题。为此，采用面向对象Petri网，引入对象Agent，对动态合同网协议进行建模,并采用Petri网的数学分析方法对模型进行了分析，表明模型具有通用性、并发性、活性的特点且通信量减少。     

Holonic coordination obtained by joining the contract net protocol with constraint satisfaction

Present manufacturing systems are facing significant challenges concerning their adaptability. Holonic manufacturing systems are among the technologies that can provide solutions to such requests, if certain conditions are met. As being included in the class of semi-heterarchical control architectures, holonic systems need appropriate coordination and planning schemes, together with validation tools to increase the beneficiaries’ trust. This paper proposes a coordination scheme for holonic systems, based on a mix between contract net protocol and distributed constraint satisfaction problems. The distinct phases of this method are explained, with details referring to the adaptation of contract net protocol. About the constraint satisfaction mechanism, a guide is provided on how a manufacturing problem can be expressed according to this formalism. To validate the introduced coordination scheme, a coloured Petri net model was developed. This allowed several simulation experiments for scenarios regarding a manufacturing system with four robots to be carried out. The obtained solutions showed that the proposed method can determine both the right holarchy related to the manufacturing goal, and optimal plans for robots. Moreover, as proven by the reachability graphs obtained for different goals, the proposed method reached correct results for all goals and diverse constraints, and it determined all possible solutions. An advantage is about how knowledge possessed by different types of holons is efficiently used, without producing an increased communication load. In conclusion, our method can ensure the right trade-off between complexity and optimality, and the attached model can constitute the required link between design and implementation, thus contributing to an easier deployment of holonic systems.     

基于规范的多agent协同机制研究*

针对传统合同网自身的局限性和存在的问题,提出了基于规范的合同网协议。首先对规范在组织符号学理论和现有的规范分类基础上,提出了层次、类型和柔性的三维规范分类;在规范的基础上对合同协议进行扩充,提出基于规范的协同过程。该协同框架由两大层次和五个阶段构成,为agent协同提供了一个柔性的解决方案,以此提高MAS中多agent协同的效率和效用。     

A tentative commit protocol for composite web services

Composite web services provide promising prospects for conducting cross-organizational business transactions. Such transactions: are generally complex, require longer processing time, and manipulate financially critical data. It is therefore crucial to ensure stronger reliability, higher throughput and enhanced performance of transactions. In order to meet these requirements, this paper proposes a new commit protocol for managing transactions in composite web services. Specifically, it aims to improve the performance by reducing network delays and the processing time of transactions. The proposed protocol is based on the concept of tentative commit that allows transactions to tentatively commit on the shared data of web services. The tentative commit protocol avoids resource blocking thus improving performance. The proposed protocol is tested through various simulation experiments. The outcomes of these experiments show that the proposed protocol outperforms existing protocols in terms of transaction performance.     

一种基于投标结果修正的合同网协议

合同网协议是一种广泛应用于多Agent系统的合作协议. 针对传统的合同网协议, 提出一种基于投标结果修正的合同网协议, 并论述该协议的合作过程, 说明该协议简化了传统合同网协议的工作过程. 最后把该协议应用于一个风力/太阳能互补发电系统的实例中, 结果表明该协议的工作效率比传统合同网协议更高.     

异步Web服务及其在.NET中的实现

随着Web服务应用范围的不断扩展,灵活的消息传递机制在许多复杂网络应用中变得越来越重要。针对目前Web服务同步调用机制存在的不足,提出了异步Web服务的解决方案。分析了异步Web服务消息传递机制,以及在．NET框架中实现异步Web服务的原理,并通过实例探讨了异步Web服务在．NET框架中的实现方法。     

合同网协议协商机制收敛性与收敛速率分析

针对合同网协议协商机制缺乏问题求解质量与效率分析的情况,设定假设条件,构建马尔可夫链模型,得出了利用目前已有的合同类型无法保证全局收敛的结论.在此基础上,提出了变邻域合同系的概念,通过分析控制方式对收敛性的影响,得出了集中式控制可以保证全局收敛以及分布式控制以概率保证全局收敛的结论,并设计了概率的计算方法.采用Doebin理论,对应用变邻域合同系的收敛速率进行分析,得出了集中式控制收敛速率与分布式控制收敛速率的上下界估计.     

MAS中基于任务聚类合同网的自主重构技术*

为了保证嵌入式实时计算系统的可靠性,提出了一种基于多智能体的嵌入式自主重构技术。首先描述了可重构MAS的组织结构,在此基础上,通过对故障节点上的任务进行聚类划分,采用基于任务聚类的合同网协商机制实现任务的再分配,提高系统的并行处理能力;同时,系统为上层用户提供透明的通信机制,屏蔽节点重构对于任务通信的影响,保证对协作式多任务可重构支持。     

Neural networks-based adaptive bidding with the contract net protocol in multi-robot systems

This paper investigates the effectiveness of using the Contract Net Protocol, an auction type system, for controlling task allocation among a group of robots, and presents and evaluates a strategy of using Artificial Neural Networks to formulate adaptive bids within the framework of the Contract Net Protocol. The robots were used in a foraging environment and showed that excellent communication among robots leads to a need for a social control mechanism for managing the robots, such as the Contract Net Protocol. The experiments also confirmed that a moderate benefit can be gained by using adaptive bidding within the framework of the Contract Net Protocol.     

基于扩展合同网协议的无线传感器网络协作方法研究

提出一种适用于无线传感器网络协作的扩展合同网协议.该协议在传统合同网协议中引入了信任度、阈值和优先级等策略,减少了无线传感器网络的通信开销,有效均衡了节点的能量消耗.为确保扩展合同网协议的完整性、正确性和可靠性.利用面向对象Petri网对其进行建模、分析和验证.仿真结果表明,扩展合同网协议有效地延长了网络生命周期,提高了网络的能耗效率,网络完成任务数也有了显著的增加.     

A pattern-based approach to protocol mediation for web services composition

ContextWith the increasing popularity of Service Oriented Architecture (SOA), service composition is gaining momentum as the potential silver bullet for application integration. However, services are not always perfectly compatible and therefore cannot be directly composed. Service mediation, roughly classified into signature and protocol ones, thus becomes one key working area in SOA.ObjectiveAs a challenging problem, protocol mediation is still open and existing approaches only provide partial solutions. Further investigation on a systematic approach is needed.MethodsIn this paper, an approach based on mediator patterns is proposed to generate executable mediators and glue partially compatible services together. The mediation process and its main steps are introduced. By utilizing message mapping, a heuristic technique for identifying protocol mismatches and selecting appropriate mediator patterns is presented. The corresponding BPEL templates of these patterns are also developed.ResultsA prototype system, namely Service Mediation Toolkit (SMT), has been implemented to validate the feasibility and effectiveness of the proposed approach.ConclusionThe approach along with the prototype system facilitate the existing practice of protocol mediation for Web services composition.     

Context-aware agents for user-oriented web services discovery and execution

Service-oriented computing (SOC) suggests that the Internet will be an open repository of many modular capabilities realized as web services. Organizations may be able to leverage this SOC paradigm if their employees are able to ubiquitously incorporate such capabilities and their resulting information into their daily practices. It is impractical to assume that human users will be able to manually search vast distributed repositories at real-time. This paper presents an architecture, Software Agent-Based Groupware using E-services (SAGE), that incorporates the use of intelligent agents to integrate human users with web services. SAGE provides background search and discovery approaches, thus enabling human users to exploit service-based capabilities that were previously too time-consuming to locate and integrate. We present a multi-agent system where each agent learns the rule-based preferences of a human user with regards to their current operational “context” and manages the incorporation of relevant web services. Recommended by: Djamal Benslimane and Zakaria Maamar     

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.     

Lifetime service level agreement management with autonomous agents for services provision

In the web services environment, service level agreements (SLA) refers to mutually agreed understandings and expectations between service consumers and providers on the service provision. Although management of SLA is critical to wide adoption of web services technologies in the real world, support for it is very limited nowadays, especially in web service composition scenarios. There lacks adequate frameworks and technologies supporting various SLA operations such as SLA formation, enforcement, and recovery. This paper presents a novel agent-based framework which utilises the agents’ ability of negotiation, interaction, and cooperation to facilitate autonomous SLA management in the context of service composition provision. Based on this framework, mechanisms for autonomous SLA operations are proposed and discussed. Results from simulations show that by integrating agents and web services the framework can address issues of SLA management drawn from sophisticated service composition scenarios.     

A high performance backoff protocol for fast execution of composite web services

Using web services to expose applications over the Internet is now a widely accepted practice. Currently, there are several ongoing efforts that provide ways to effectively compose web services distributed across different organizations. One of the problems underlying the deployment of such composite services on the web, however, is service co-allocation that arises when a composite service needs to ensure all the required component services to be available for execution at the same time. Motivated by this, this paper presents a new decentralized protocol, named web service co-allocation protocol (WSCP), which can facilitate fast execution of composite web services. The proposed framework is an enhancement of the famous two phase commit protocol through the incorporation of tentative hold phase as well as the employment of a new high performance backoff protocol developed to better address the dynamics of the service co-allocation problem. The simulation results show that the proposed approach yields significant improvements over existing protocols.