A Market-Oriented Grid Directory Service for Publication and Discovery of Grid Service Providers and their Services

The emergence of Grids as a platform for sharing and aggregation of distributed resources increases the need for mechanisms that allow an efficient management of resources. The Grid economy has been identified as one of the potential solutions as it helps in managing the supply and demand for resources and enables sustained sharing of resources by providing economic incentive for Grid resource providers. An economy based Grid computing environment needs to support an infrastructure that enables the creation of a marketplace for meeting of providers and consumers. This paper presents the Grid Market Directory (GMD) that serves as a registry for publication and discovery of Grid service providers and their services.     

网格经济模型中基于信任机制的调度算法

在网格环境中使用经济学原理进行资源管理和调度是网格从理论研究走向实际应用的有效途径之一。本文在Buyya设计的GRACE网格资源管理框架下,提出一种基于微分方程的信任值量化计算公式:信任=直接信任8声誉,在此基础上建立基于行为的网格信任机制。根据应用环境的不同需求,对网格经济模型调度算法(DBC)进行改进,分别提出了以时间优化、成本优化和时间成本折衷优化为目的的网格信任调度算法(TrustDBC)。理论分析及模拟实验结果表明,本文算法性能明显优于相应的未考虑信任的调度算法。     

A brokerage system for solar data archives

Scientific research and practical applications of solar physics require data and computational services to be integrated seamlessly and efficiently. The European Grid for Solar Observations (EGSO) leverages Grid‐oriented concepts and technology to provide a high‐performance infrastructure for solar applications. In this paper, an architecture for a data brokerage service is proposed. Brokers interact with providers and consumers in order to build a profile of both parties. In particular, a broker interacts with providers in order to gather information on the data potentially available to consumers, and with the consumers in order to identify the set of providers that are most likely to satisfy specific data needs. The brokerage technique is based on a multi‐tier management of metadata. Copyright © 2006 John Wiley & Sons, Ltd.     

网格资源管理中的经济学原理运用

网格的目标是实现对地理上广泛分布的大量异构资源进行共享。由于网格具有的异构性、分布性和动态性,传统的资源管理方法在网格环境中并不适用。此外,要吸引各类资源消费者和提供者加入网格,就必须满足他们各自的需求。将经济学原理,例如边际效用、Nash均衡等引入网格资源管理之中,能够很好地解决以上问题。该文简略地列举了近10年来在分布式系统上使用经济学模型进行资源分配的相关研究,并且对目前开展得比较好的几个网格经济学研究项目进行了分析。     

网格环境下基于D-S证据理论的信誉评价模型

在深入分析相关信誉问题研究的基础上,结合网格环境以及在此方面同行所做前沿工作,通过引入Dempster-Shafer证据理论,提出一种新的支持网格的信誉评价模型,给出相应的信誉评价模型及算法.仿真结果表明,该模型较好地解决了网格实体信誉定量评价问题,具有良好的网格动态适应性及鉴别信誉欺骗行为的能力.     

网格环境下一种基于模糊偏序关系的可信资源选择方法

网格环境下的资源选择问题因为选择范围广、实体陌生程度高而颇具挑战性。高效资源共享和使用离不开高可信性的保障。将信誉机制引入网格环境下的资源选择,旨在于提高可信性和可靠性保障。根据信誉的多客面性和不确定性,以模糊偏序关系上的评估决策思想为指导,该方法对资源提供方的多方面信誉状况进行模糊偏序关系建模、信息融合,依据最后得到的综合排序,进行资源选择决策。与有关方法比较,该方法具有很好的统筹兼顾性。     

网格环境下的信誉评价及管理模型研究

将在分布式环境下适应的信誉评价算法进行改进使其适用于网格环境中,以网格环境下的安全合作为目标,结合网格环境以及在此方面同行所做的前沿工作,提出一种新的基于Dempster-Shafer证据理论的支持网格的信誉评价算法,以适应网格实体信誉定量评价的要求,解决网格信誉描述的不可测量性和模糊性问题,并给出相应的信誉管理模型.     

On Desideratum for B2C E-Commerce Reputation Systems

This paper reviews existing approaches to reputation systems, their constraints as well as available solutions. Furthermore, it presents and evaluates a novel and comprehensive reputation model devoted to the distributed reputation system for Business-to-Consumer (B2C) E-commerce applications that overcomes the discussed drawbacks. The algorithm offers a comprehensive approach as it considers a number of issues that have a bearing on trust and reputation such as age of ratings, transaction value, credibility of referees, number of malicious incidents, collusion and unfair ratings. Moreover, it also extends the existing frameworks based on information about past behaviour, with other aspects affecting online trading decisions which relate to the characteristic of the providers, such as existence of trustmark seals, payment intermediaries, privacy statements, security/privacy strategies, purchase protection/insurance, alternative dispute resolutions as well as the existence of first party information.     

Reputation-based dependable scheduling of workflow applications in Peer-to-Peer Grids

Grids facilitate creation of wide-area collaborative environment for sharing computing or storage resources and various applications. Inter-connecting distributed Grid sites through peer-to-peer routing and information dissemination structure (also known as Peer-to-Peer Grids) is essential to avoid the problems of scheduling efficiency bottleneck and single point of failure in the centralized or hierarchical scheduling approaches. On the other hand, uncertainty and unreliability are facts in distributed infrastructures such as Peer-to-Peer Grids, which are triggered by multiple factors including scale, dynamism, failures, and incomplete global knowledge.In this paper, a reputation-based Grid workflow scheduling technique is proposed to counter the effect of inherent unreliability and temporal characteristics of computing resources in large scale, decentralized Peer-to-Peer Grid environments. The proposed approach builds upon structured peer-to-peer indexing and networking techniques to create a scalable wide-area overlay of Grid sites for supporting dependable scheduling of applications. The scheduling algorithm considers reliability of a Grid resource as a statistical property, which is globally computed in the decentralized Grid overlay based on dynamic feedbacks or reputation scores assigned by individual service consumers mediated via Grid resource brokers. The proposed algorithm dynamically adapts to changing resource conditions and offers significant performance gains as compared to traditional approaches in the event of unsuccessful job execution or resource failure. The results evaluated through an extensive trace driven simulation show that our scheduling technique can reduce the makespan up to 50% and successfully isolate the failure-prone resources from the system.     

Performance analysis of allocation policies for interGrid resource provisioning

Several Grids have been established and used for varying science applications during the last years. Most of these Grids, however, work in isolation and with different utilisation levels. Previous work has introduced an architecture and a mechanism to enable resource sharing amongst Grids. It has demonstrated that there can be benefits for a Grid to offload requests or provide spare resources to another Grid. In this work, we address the problem of resource provisioning to Grid applications in multiple-Grid environments. The provisioning is carried out based on availability information obtained from queueing-based resource management systems deployed at the provider sites which are the participants of the Grids. We evaluate the performance of different allocation policies. In contrast to existing work on load sharing across Grids, the policies described here take into account the local load of resource providers, imprecise availability information and the compensation of providers for the resources offered to the Grid. In addition, we evaluate these policies along with a mechanism that allows resource sharing amongst Grids. Experimental results obtained through simulation show that the mechanism and policies are effective in redirecting requests thus improving the applications’ average weighted response time.     

Explanation-aware service selection: rationale and reputation

A collection of 1 billion¹ publicly available web services can form an internet-scale infrastructure for building diverse applications. For a given application, selection of services and service providers from this collection becomes important and reputation is recognized as a key factor for this purpose. However, current reputation systems are limited in their ability to exchange reputation information between heterogeneous systems. To facilitate meaningful exchange and reuse of reputation information and for the overall determination of reputation, we identify the need to infer and explicate rationale for ratings. We present our knowledge-based approach to inferring and explicating rationale for ratings. We show that this approach facilitates detection of deception and collusion, user preference elicitation, explication of rationale behind user ratings and generation of personalized service recommendations.     

An optimization-based adaptive resource management framework for economic Grids: A switching mechanism

The application of Grid computing has been broadening day by day. An increasing number of users has led to the requirement of a job scheduling process, which can benefit them through optimizing their utility functions. On the other hand, resource providers are exploring strategies suitable for economically efficient resource allocation so that they can maximize their profit through satisfying more users. In such a scenario, economic-based resource management strategies (economic models) have been found to be compelling to satisfy both communities. However, existing research has identified that different economic models are suitable for different scenarios in Grid computing. The Grid application and resource models are typically very dynamic, making it challenging for a particular model for delivering stable performance all the time. In this work, our focus is to develop an adaptive resource management architecture capable of dealing with multiple models based on the models’ domains of strengths (DOS). Our preliminary results show promising outcomes if we consider multiple models rather than relying on a single model throughout the life cycle of a Grid.     

A multicriteria approach to two-level hierarchy scheduling in grids

In this paper we address a multicriteria scheduling problem for computational Grid systems. We focus on the two-level hierarchical Grid scheduling problem, in which at the first level (the Grid level) a Grid broker makes scheduling decisions and allocates jobs to Grid nodes. Jobs are then sent to the Grid nodes, where local schedulers generate local schedules for each node accordingly. A general approach is presented taking into account preferences of all the stakeholders of Grid scheduling (end-users, Grid administrators, and local resource providers) and assuming a lack of knowledge about job time characteristics. A single-stakeholder, single-criterion version of the approach has been compared experimentally with the existing approaches.     

基于信誉系统对GRID网格Leader选择协议的安全性研究

针对GRID路由协议中的网格Leader选择协议,首先运用基于有限状态机的形式化分析方法对它的安全性进行了分析,之后基于现有信誉系统,提出一种基于信誉度的信誉模型。模型包括信誉度计算、信誉管理和信誉决策,依据节点信誉度的变化以及设置的信誉度阈值识别并处理内部恶意节点,保证网络通信的安全可靠。仿真实验表明,该模型能够有效识别出恶意节点,显著提高网络分组投递率,但节点间传输平均时延有所延长,需进一步优化。     

Towards the integration of reputation management in OpenID

OpenID is an open standard providing a decentralized authentication mechanism to end users. It is based on a unique URL (Uniform Resource Locator) or XRI (Extensible Resource Identifier) as identifier of the user. This fact of using a single identifier confers this approach an interesting added-value when users want to get access to different services in the Internet, since users do not need to create a new account on every website they are visiting. However, OpenID providers are normally used as a point to store certain personal attributes of the end users too, which might be of interest for any service provider willing to make profit from collecting that personal information. The definition of a reputation management solution integrated as part of the OpenID protocol can help users to determine whether a given service provider is more or less reliable before interacting with it and transferring their private information. This paper is providing the definition of a reputation framework that can be applied to the OpenID SSO (Single Sign-On) standard solution. It also defines how the protocol itself can be enhanced so OpenID providers can collect (and provide) recommendations from (to) users regarding different service providers and thus enhancing the users' experience when using OpenID. Besides the definition, a set of tests has been performed validating the feasibility of the framework.     

Managing Role-Based Access Control Policies for Grid Databases in OGSA-DAI Using CAS

In this paper, we present a role-based access control method for accessing databases through the Open Grid Services Architecture – Data Access and Integration (OGSA-DAI) framework. OGSA-DAI is an efficient Grid-enabled middleware implementation of interfaces and services to access and control data sources and sinks. However, in OGSA-DAI, access control causes substantial administration overhead for resource providers in virtual organizations (VOs) because each of them has to manage a role-map file containing authorization information for individual Grid users. To solve this problem, we used the Community Authorization Service (CAS) provided by the Globus Toolkit to support the role-based access control (RBAC) within OGSA-DAI. CAS uses the Security Assertion Markup Language (SAML). Our method shows that CAS can support a wide range of security policies using role-privileges, role hierarchies, and constraints. The resource providers need to maintain only the mapping information from VO roles to local database roles and the local policies in the role-map files, so that the number of entries in the role-map file is reduced dramatically. Also, unnecessary authentication, mapping and connections can be avoided by denying invalid requests at the VO level. Thus, our access control method provides increased manageability for a large number of users and reduces day-to-day administration tasks of the resource providers, while they maintain the ultimate authority over their resources. Performance analysis shows that our method adds very little overhead to the existing security infrastructure of OGSA-DAI.     

对等网络信誉机制研究综述

随着电子商务、网格、对等网络的流行，信誉机制被作为一种新颖的安全问题解决方案，在国际上得到广泛研究，并取得许多重要成果,本文主要介绍面向对等网络的信誉机制的发展情况，提出一个基本框架模型，对信誉系统设计做了初步探讨，并分析了当前一些重要研究成果，比较了他们的优点和不足,最后，概述性归纳了目前对等网络的信誉机制研究中遇到的问题，并提出一些可能的解决思路和看法．     

网格环境中用于资源分配的经济模型研究

由于网格是实现对地理上广泛分布的大量异构资源进行共享，所以传统的资源调度和分配方法已经不再适用。此外为了吸引各类资源消费者和资源提供者加入网格，必须引入基于价格的经济模型，由价格浮动来反映资源供需情况的动态变化，通过供需均衡实现资源优化分配。该文讨论了现有的用于资源分配的各种经济模型以及各自的优缺点，最后总结了判断经济模型效能的各种经济和计算标准。     

用P2P技术改进网格信息服务

本文根据网格资源信息的特点阐述了由高度分布式的信息提供者和集合目录组成的网格信息服务基本框架。并分析了它的基础LDAP（Lightweight Directory Access Protocol）协议，指出LDAP目录本质是一种分布式的数据库。由于网格信息系统中LDAP目录信息树的动态刷新与复制的频繁发生，我们已提出用环形扩展和线形扩展策略来大幅度提高系统效率；在此基础上，本文进一步提出了文件分块复制法的思想把LDAP数据库文件分成若干块，在多个LDAP服务器端点间并行复制，最后实践证明，它大幅度提高了以LDAP目录分布式数据库为基础与核心的网格信息服务系统的并行效率。     

基于D—S理论的网格信任模型

信任机制已经被广泛地应用于网格计算。基于网格节点对于资源提供的反馈评价,提出了一种基于Dempster—Sharer证据理论的网格信任模型。该模型给出信任函数、似然函数、信任损失的表示方法,并在此基础上建立了对于资源提供者的信任监测机制及防止资源使用者共同串谋与诋毁的方法。