P2P数据库系统研究

新兴的P2P技术由于体现出许多新的特性及优点,一直受到工业界和学术界的共同关注。数据共享是P2P技术应用较多的领域之一,但大家所熟悉的P2P应用系统提供的是文件层次的数据共享,不能满足诸如关系型数据等结构化数据的共享需求,而数据库领域的传统数据集成方法在某些特定情形下难以实施。针对这一问题,P2P技术与数据库技术的结合成了解决问题的一条途径。本文介绍了P2P数据库系统产生的背景,并主要从P2P技术的特点和P2P重叠网络的分类两个方面简单介绍了P2P技术,重点分析P2P数据库与分布式数据库的异同点。然后介绍了一种P2P数据库系统原型实例——PeerDB。最后进行了简单的总结及展望。     

对等计算技术在流媒体直播系统中的应用

对等计算（Peer-To-Peer,简称P2P）由于在文件交换、视频直播、即时通讯等领域的广泛应用．成为计算机界内热门关注的话题之一。本文从对等计算的基本定义、工作原理等方面来说明其在目前网络中使用频率较高的流媒体直播系统中的应用。     

移动商务推荐系统中的一种基于P2P的隐私保护策略

近年来,移动推荐系统已成为推荐系统研究领域最活跃的课题之一。但由于移动终端的私人性和移动网络的复杂性,在保证高精度推荐的同时如何保护用户隐私已经成为移动商务发展的主要挑战。传统推荐系统中的隐私保护技术由于移动终端的计算能力差、无线网络的带宽弱等局限无法适用于移动商务推荐系统。针对以上问题,面向移动商务推荐提出一种基于P2P的隐私保护策略,通过构建P2P好友圈,采用基于k-匿名的代理转发的增量数据更新方式,实现不对增量数据进行任何修改以保证高精度推荐,同时保护用户隐私安全。最后通过实验验证了基于P2P的隐私保护策略的可行性和推荐服务的有效性。     

基于语义路由的P2P系统综述

介绍了P2P系统的发展状况，归纳了典型的结构化P2P系统模型，对结构化P2P系统中的节点拓扑结构、语义路由算法、数据存储和共享、应用层多播等热点问题进行了讨论，介绍了非结构化P2P系统的语义路由过程，总结了当前主要的基于语义路由P2P系统的优缺点，并据此提出了该领域的发展趋势。     

P2P资源搜索技术综述

对等(P2P)计算作为近年来兴起的一种重要的分布式计算模式,在很多领域都有着大量的应用和研究。随着越来越多的数据存储到P2P系统中,上层应用就需要底层架构来提供关键的数据定位和搜索能力,所以P2P资源搜索技术是P2P系统中的一种非常关键的技术,P2P资源搜索技术涉及到P2P系统的很多方面。例如资源定位所需要的时间,消耗的带宽等等。本文主要总结了当前P2P系统使用的几种重要的搜索技术以及相关应用,并对此进行总结,从而为研究P2P资源搜索提供思路和方法。     

基于分组式P2P网络的空间区域查询

针对传统集中式空间数据应用出现的性能瓶颈以及结构化P2P系统中由于数据的一致性分布而导致的空间数据物理特性丢失等问题,提出一种分组式P2P网络系统,并描述在该网络系统下的数据插入和删除、节点的加入和离开以及空间区域查询。通过仿真验证了其有效性。     

移动P2P数据分发技术研究*

移动P2P数据分发技术将P2P模型应用到移动网络中,通过节点间的相互配合来提高系统的可靠性、传输速度和扩展性,目前已成为无线通信的重点研究领域。但是由于移动网络的复杂性,现有的移动P2P数据分发技术在实际应用中仍然存在很多问题。对近年来该领域的一些重点技术如Gossip算法、网络编码、纠错码进行了介绍,并在可靠性、传输速度和扩展性方面对它们进行了分析,针对其在网络动态适应性、网络融合、节点合作度等方面的不足提出了今后的研究方向。     

P2P和Grid从构建到应用全历程对比

网格和P2P网络技术均是当今高性能分布式计算领域的研究热点。从体系结构、资源管理、安全和应用等方面对这两种新兴技术进行了全方位的比较,发现了由于P2P和Grid的侧重点不同,P2P和Grid从构建到投入应用都有不同程度的互补性。这使得糅合P2P与Grid可以构建一个兼具P2P和Grid特性的新型P2P-Grid系统。     

用Small-World设计无组织P2P系统的路由算法

由于peer-to-peer系统在件共享方面有着巨大的应用前景，peer-to-peer搜索问题已成为目前学术界重点的研究问题之一．对于缺乏缓存机制的无组织P2P系统。已有的分布式路由算法缺乏全局导航能力，属于无序搜索．为此，提出一种key clustering算法，将路由空间分为HUB和AUT两层，从全局角度进行有序搜索．为提高key clustering算法的可扩展性，借鉴Small-world领域的研究成果，在路由表中以一定概率插入连接远距离节点的快捷连接，以缩短平均路径长度．初步仿真实验表明，引入快捷连接的key clustering算法具有良好的搜索能力和扩展性。     

一种新的基于P2P系统的网格资源信息发现方法

网格环境下,众多的资源中查找发现所需的资源是一个关键的问题.基于结构化的支持数据顺序索引的P2P系统提出了一种全新的网格环境下资源发现的方法,该方法将数据库领域先进的多维数据索引技术Pyramid引入到P2P系统之中.通过数据库的多维索引技术,使得P2P系统支持网格资源的多维范围查询.该算法采用了对称结构的金字塔技术,使得网格资源管理动态属性变化的维护代价方面具有很好的性能..理论证明,当维度较大时,由于属性动态性导致的维护代价与维度成反比,而与属性的变化范围无关.另外对P2P的负载均衡策略进行了相应的考虑.最后,对系统的路由性能以及范围查询的有效性进行了仿真验证.     

A survey on Security Issues of Reputation Management Systems for Peer-to-Peer Networks

The objective of this paper is to present a comprehensive survey of security issues in Reputation based Trust Management system (RTMS) also known in short as Reputation Management Systems for P2P networks. The wide adoption of P2P computing has enhanced content publishing, pervasive information collection, streaming of real-time sensed data and information sharing on an enormous global scale. At the same time, the open and anonymous nature of P2P makes it vulnerable to malicious attacks and the spread of malware. In this paper, we discuss in detail the different security attacks on P2P systems and have categorized them as network-related and peer-related attacks. RTMS helps to establish and evaluate Trust, which is the degree of belief that is established to prove that the right user is accessing the right resource. We have explained the different Trust Management schemes used in P2P networks and have compared them on the basis of trust establishment, security features, trust evaluation and weakness. We have surveyed the RTMSs currently in use and have compared them on the basis of reputation collection, aggregation, computation, storage and degree of centralization of reputation computation and management. We also present a comparison of protection provided by RTMs against the various security attacks discussed. Open research issues and challenges that have yet to be addressed in the design of current RTMs have been presented in detail. This survey can be used as a reference guide to understand Trust Management and RTMS for P2P networks and to further research in RTMSs to make them efficient, reliable and scalable to enable and promote the utilization of P2P systems for large communities and applications.     

Indexing views to route queries in a PDMS

P2P computing gains increasing attention lately, since it provides the means for realizing computing systems that scale to very large numbers of participating peers, while ensuring high autonomy and fault-tolerance. Peer Data Management Systems (PDMS) have been proposed to support sophisticated facilities in exchanging, querying and integrating (semi-)structured data hosted by peers. In this paper, we are interested in routing graph queries in a very large PDMS, where peers advertise their local bases using fragments of community RDF/S schemes (i.e., views). We introduce an original encoding for these fragments, in order to efficiently check whether a peer view is subsumed by a query. We rely on this encoding to design an RDF/S view lookup service featuring a statefull and a stateless execution over a DHT-based P2P infrastructure. We finally evaluate experimentally our system to demonstrate its scalability for very large P2P networks and arbitrary RDF/S schema fragments, and to estimate the number of routing hops required by the two versions of our lookup service. Work done when T. Dalamagas was a postdoc researcher in NTUA.     

井场数据一体化集成方案对比分析

阐明了分专业数据集成管理、两级数据集成管理和一级数据集成管理三种方案的优缺点,并从系统架构、数据采集、数据存储和对应用系统的支持四个方面对三种方案进行了全面对比分析。     

Industrial applications of type-2 fuzzy sets and systems: A concise review

Data, as being the vital input of system modelling, contain dissimilar level of imprecision that necessitates different modelling approaches for proper analysis of the systems. Numbers, words and perceptions are the forms of data that has varying levels of imprecision. Existing approaches in the literature indicate that, computation of different data forms are closely linked with the level of imprecision, which the data already have. Traditional mathematical modelling techniques have been used to compute the numbers that have the least imprecision. Type-1 fuzzy sets have been used for words and type-2 fuzzy sets have been employed for perceptions where the level of imprecision is relatively high. However, in many cases it has not been easy to decide whether a solution requires a traditional approach, i.e., type-1 fuzzy approach or type-2 fuzzy approach. It has been a difficult matter to decide what types of problems really require modelling and solution either with type-1 or type-2 fuzzy approach. It is certain that, without properly distinguishing differences between the two approaches, application of type-1 and type-2 fuzzy sets and systems would probably fail to develop robust and reliable solutions for the problems of industry. In this respect, a review of the industrial applications of type-2 fuzzy sets, which are relatively novel to model imprecision has been considered in this work. The fundamental focus of the work has been based on the basic reasons of the need for type-2 fuzzy sets for the existing studies. With this purpose in mind, type-2 fuzzy sets articles have been selected from the literature using the online databases of ISI-Web of Science, ScienceDirect, SpringerLink, Informaworld, Engineering Village, Emerald and IEEE Xplore. Both the terms “type-2 fuzzy” and “application” have been searched as the main keywords in the topics of the studies to retrieve the relevant works. The analysis on the industrial applications of type-2 fuzzy sets/systems (FSs) in different topics allowed us to summarize the existing research areas and therefore it is expected be useful to prioritize future research topics. This review shows that there are still many opportunities for application of type-2 FSs for several different problem domains. Shortcomings of type-1 FSs can also be considered as an opportunity for the application of type-2 FSs in order to provide a better solution approach for industrial problems.     

Supporting engineering applications by new data base processing concepts—An experience report

Data base management systems for nonstandard applications (nonstandard data base systems, NDBS), in particular for engineering applications, nowadays constitute one of the most important challenges in the area of data base research. Some major obstacles are concerned with problems of modeling and processing complex engineering objects. Some new system architectures have been proposed, and appropriate concepts for handling the new types of application objects have been developed over the past few years.Based on PRIMA, an NDBS-kernel prototype implementation, we motivate a workstation-oriented architecture for NDBS application systems. We explain a prototypical application system in the environment of VLSI-chip design, which serves as a practical examples in handling complex objects. Analyzing the weaknesses of this initial approach, we derive general concepts for application linkage, discussing, in particular, key issues for an efficient object processing and language binding.     

A compiler model for a relational data base management system

One of the chief difficulties which needs to be overcome during the early design stages of a system is that of establishing a satisfactory design for that system. From the time it was first conceived it was apparent that the Relational Data Base Management System is like a compiler in so far as it takes a succession of user requests for information formulated in an applied predicate calculus and translates each one into a series of calls which access an underlying data base and transform data from that data base into the form the user wishes to see. This paper compares the architecture of the Relational Data Base Management System with that of a compiler, and then demonstrates the use of the architecture when processing a language based on an applied predicate calculus. Finally, the paper describes a number of extensions to that architecture which are required to solve the particular problems raised by the data base system.     

数据网格中的数据复制技术研究

数据复制技术是数据网格系统中广泛采用的改善网格系统性能的关键技术之一。与传统分布式系统应用领域中的复制相比，数据网格中的复制技术在复制目标、复制粒度、复制关键技术等方面表现出独特性质。本文将数据复制技术概括为副本创建、数据传输、副本删除、副本选择、副本一致性管理、安全管理等环节，深入分析、探讨了数据网格系统中数据复制的各项关键技术，为建立综合的数据网格复制策略和技术框架提供了全面的技术分析。最后，对数据复制技术下一步的研究方向作了分析和预测。     

Sophia: A local trust system to secure key-based routing in non-deterministic DHTs

Today, many distributed applications are typically deployed at a large scale, including Grid, web search engines and content distribution networks, and it is expected for their scale to grow more in terms of number of machines, locations and administrative domains. This poses many scalability issues related to the scale of the environment they run in. To explicitly address these issues, many distributed systems and everyday services use peer-to-peer (P2P) overlays to allow other parts of the system to benefit from the fault-tolerance and scalability of P2P technology. In particular, Distributed Hash Tables (DHTs), which implement a simple put-and-get interface to a dictionary-like data structure, have been extensively used to overcome the current limitations associated with the centralized and hierarchical components of distributed systems, including data management, resource discovery, job scheduling etc.     

一种多自治域层次互操作模型的系统框架

数据互操作是信息集成领域需要解决的关键问题。联邦数据库和多数据库是解决分布式异构环境中多个数据源的集成与互操作的两种方法,但它们各有优缺点。完全的集中不能保证局部系统的自治,全部的分散又不能保证系统之间的共享和互操作。在分析联邦数据库与多数据库特点与差异的基础上,提出了一种多自治域的层次互操作模型MDHI,通过对Panorama多数据库系统进行扩展,给出了一种基于WebService的PanoramaWebOne系统框架。这种框架既满足了局域范围内的集成和处理效率,又提供了一种集成广域范围内多种异构数据源的方法,更加符合当前实际应用的需要。     

基于业务分割的并行式大数据迁移策略研究

 大数据处理是目前研究的一个热点问题,大数据给数据存储、数据管理、数据检索带来巨大的挑战,它对存储硬件、存储策略、检索方法等研究提出了更高的要求。针对大数据处理问题,提出基于业务分割的、并行式数据迁移策略,并在此基础上开发数据迁移平台。实验结果表明：该平台在数据访问速度、占用系统内存等方面,比传统的数据迁移方法拥有更大的优势。目前该平台已在某银行收支核查系统中取得了很好的使用效果。