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A Framework for Supporting Tree-Like Indexes on the chord Overlay

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Journal of Computer Science & Technology 2013年第6期28卷 962-972页

作者：朱命冬申德荣寇月聂铁铮于戈 CCF ACM College of Information Science and EngineeringNortheastern University IEEE

With the explosive growth of data, to support efficient data management including queries and updates, the database system is expected to provide tree-like indexes, such as R-tree, M-tree, B＋-tree, according to different types of data. In the distributed environment, the indexes have to be scattered across the compute nodes to improve reliability and scalability. Indexes can speed up queries, but they incur maintenance cost when updates occur. In the distributed environment, each compute node maintains a subset of an index tree, so keeping the communication cost small is more crucial, or else it occupies lots of network bandwidth and the scalability and availability of the database system are affected. Further, to achieve the reliability and scalability for queries, several replicas of the index are needed, but keeping the replicas consistent is not straightforward. In this paper, we propose a framework supporting tree-like indexes, based on chord overlay, which is a popular P2P structure. The framework dynamically tunes the number of replicas of index to balance the query cost and the update cost. Several techniques are designed to improve the efficiency of updates without the cost of performance of the queries. We implement M-tree and R-tree in our framework, and extensive experiments on real- life and synthetic datasets verify the efficiency and scalability of our framework.

关键词： tree-like index chord distributed algorithm

A chord-based resource scheduling approach in drug discovery grid

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High Technology Letters 2007年第1期13卷 36-41页

作者：陈曙东 Zhang Wenju　 Zhang Jun 　 Ma Fanyuan Shen Jianhua Department of Computer Science and Engineering Shanghai Jiaotong University Shanghai 200030 P.R. China Jiangnan Institute of Computing Technology Wuxi 214083 P.R. China Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 200031 P. R. China

This paper presents a resource scheduling approach in grid computing environment. Using P2P technology, this novel approach can schedule dynamic grid computing resources efficiently. Grid computing resources in different domains are organized into a structured P2P overlay network. Available resource information is published in type of grid services. Task requests for computational resources are also presented as grid services. Problem of resources scheduling is translated into services discovery. Different from central scheduling approaches that collect available resources information, this chord-based approach forwards task requests in the overlay network and discovers satisfied resources for these tasks. Using this approach, the computational resources of a grid system can be scheduled dynamically according to the real- time workload on each peer. Furthermore, the application of this approach is introduced into DDG, a grid system for drug discovery and design, to evaluate the performance. Experimental results show that computational resources of a grid system can be managed efficiently, and the system can hold a perfect load balance state and robustness.

关键词： grid computing P2P chord resource scheduling

Cross-layer optimized chord protocol for separated ring convergence in MANET

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The Journal of China Universities of Posts and Telecommunications 2009年第4期16卷 84-90页

作者： MEI Jing-qing JI Hong LI Ting Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

An optimized chord protocol is proposed to solve the convergence problem for separated chord rings over mobile Ad-hoc networks （MANETs）. This protocol exploits the information of topological neighbors in routing layer by utilizing a cross-layer design, and periodically detects whether there is any neighbor node that belongs to an alien chord ring by sending detecting packets. The detection will be confirmed and then the corresponding predecessor node will be found out to initialize convergence of the chord rings. Theoretical analysis and experiment results show that the proposed algorithm can detect separated chord rings and implement the convergence process efficiently, and that a significant improvement in the successful lookup ratio is also achieved at an acceptable overhead for the system maintenance. Moreover, the proposed protocol can ensure the stability and scalability of the system.

关键词： convergence chord mobile Ad-hoc network (MANET) cross-layer

Exact number of chord diagrams and an estimation of the number of spine diagrams of order n

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Chinese Science Bulletin 1997年第9期42卷 705-718页

作者： Li, BH Sun, HW Institute of Systems Science Chinese Academy of Sciences Beijing China

The main results are as follows:( i ) For the number of chord diagrams of order n, an exact formula is given.( ii ) For the number of spine diagrams of order n, the upper and lower bounds are obtained. These bounds show that the estimation is asymptotically the *** a byproduct, an upper bound is obtained, for the dimension of Vassiliev knot invariants of order n, that is, 1/2 ( n -1)! for any n≥3, and 1/2( n - 1)! - 1/2( n - 2)! for bigger n . Our upper bound is based on the work of Chmutov and Duzhin and is an improvement of their bound ( n - 1)! . For n = 3, and 4,1/2( n - 1)! is already the best.

关键词： knot Vassiliev invariant chord diagram spine diagram combinatorics.

Tachord: a chord system using topology-aware routing and super peers

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Journal of Southeast University(English Edition) 2004年第3期20卷 273-278页

作者：陈东锋杨寿保彭小燕中国科学技术大学计算机科学技术系合肥230027

Due to minimum consideration of an actual network topology, the existing peer-to-peer (P2P) overlay networks, such as CAN, chord, Pastry and Tapestry, will lead to high latency and low efficiency. In Tachord, a topology-aware routing approach in P2P overlays and an improved design in chord are presented. Tachord and other algorithms are evaluated by physical hops, interdomain-adjusted latency, and aggregate bandwidth used per message. Experimental results demonstrate that Tachord has the drastic improvement in routing performance where average physical hop is half that of chord, and the impact of cache management strategies in the Tachord overlay cannot be neglected.

关键词： peer-to-peer network topology-aware routing super peer chord

基于chord网的语义Web Service发现

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电子学报 2007年第B12期35卷 152-155页

作者：吴万明吴毅坚赵文耘复旦大学计算机科学与工程系软件工程实验室上海210433

本文提出一个实用、高效、可扩展的新型语义WebService发现模型，将集中式的服务注册和服务发现机制分散到分布式网络结构中的各个注册节点，并引入本体概念组和服务特征向量概念．首先对服务语义本体分组，然后将服务描述和服务查询映... 详细信息

本文提出一个实用、高效、可扩展的新型语义WebService发现模型，将集中式的服务注册和服务发现机制分散到分布式网络结构中的各个注册节点，并引入本体概念组和服务特征向量概念．首先对服务语义本体分组，然后将服务描述和服务查询映射为服务特征向量进行匹配，从而提高了服务发现的效率和准确性．

关键词：语义web service web service发现 peer-to-peer chord 本体

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基于chord的多租户索引机制研究

计算机学报 2016年第2期39卷 270-285页

作者：邹立达李庆忠孔兰菊王振坤山东大学计算机科学与技术学院济南250101 山东省软件工程重点实验室济南250101

多租户数据管理是支持SaaS应用高效运行的重要组成部分.随着租户规模的不断扩大,多租户数据库需要云计算环境下的每个节点都存储并处理租户数据,因此适合利用对等结构(P2P)组织管理多租户数据.组织良好、易扩展的云中多租户索引机制是... 详细信息

多租户数据管理是支持SaaS应用高效运行的重要组成部分.随着租户规模的不断扩大,多租户数据库需要云计算环境下的每个节点都存储并处理租户数据,因此适合利用对等结构(P2P)组织管理多租户数据.组织良好、易扩展的云中多租户索引机制是高效查询的关键.文中基于P2P结构对多租户索引机制展开研究,针对不同租户的索引易相互干扰、租户数据分布无序的问题,通过对chord的映射方法进行改进将所有租户索引统一映射到一个标识符空间,给出的映射函数使单个租户索引可以隔离、保序地在空间分布.同时设计了各节点所负责的标识符空间范围的分配算法,使租户索引及数据可均衡、聚集地放置在各节点,从而使查询时既能通过对等结构避免性能瓶颈,也降低了数据传输成本.文中给出了多租户索引机制的动态维护策略,提出的标识符空间增倍方法使该索引机制能够适应租户数量与索引不断增加的应用场景.实验结果表明,该机制在租户规模较大时,与集中式索引相比查询时间至少可以节省50%,吞吐量提高1.5倍.

关键词：多租户索引 P2P chord 多租户数据库标识符空间云计算

一种基于chord的完全分布式克隆TPM检测方案

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高技术通讯 2008年第11期18卷 1112-1116页

作者：郝黎明陆松年杨树堂上海交通大学电子工程系上海200240

针对直接匿名验证(DAA)协议中使用可变名字基时检测克隆可信平台模块(TPM)存在的困难,在保持 TPM 高匿名度的前提下,提出了一种基于 chord 的完全分布式克隆 TPM 检测方案。将访问服务的 TPM 映射到 chord 覆盖层中,在不依赖可信第三方(... 详细信息

针对直接匿名验证(DAA)协议中使用可变名字基时检测克隆可信平台模块(TPM)存在的困难,在保持 TPM 高匿名度的前提下,提出了一种基于 chord 的完全分布式克隆 TPM 检测方案。将访问服务的 TPM 映射到 chord 覆盖层中,在不依赖可信第三方(TTP)参与的情况下实现了对克隆 TPM 的有效检测。以服从泊松分布的 TPM 访问规律和服从负指数分布的服务时间为模型,对该方案和已有方案的性能进行了分析与仿真,结果表明该方案具有高检测率和零虚警率等特性。该检测方案思想可以在不增加额外开销的情况下部署到基于分布式哈希表(DHT)的完全分布式系统中。

关键词：克隆TPM 可信计算直接匿名验证 chord 假名

RR-chord:一个基于chord的低开销快速查询P2P系统

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北京理工大学学报 2008年第2期28卷 134-138页

作者：任小金古志民高志伟段赵磊北京理工大学计算机科学技术学院

针对结构化P2P系统高异质性和节点频繁加入或离开带来的系统性能问题,基于chord设计了一个RR-chord系统.该系统所有节点被分为路由节点和非路由节点.路由节点具有更多的资源和路由信息,并可根据自身能力的强弱调整其路由表的大小,所有... 详细信息

针对结构化P2P系统高异质性和节点频繁加入或离开带来的系统性能问题,基于chord设计了一个RR-chord系统.该系统所有节点被分为路由节点和非路由节点.路由节点具有更多的资源和路由信息,并可根据自身能力的强弱调整其路由表的大小,所有的路由节点形成路由环,所有的路由信息在路由环上路由以提高系统的查询效率.设计的新的加入算法,进一步减少了节点频繁加入与离开造成的维护开销.理论分析和实验结果表明,RR-chord具有较好的路由性能和非常低的维护开销.

关键词： P2P chord 查询