P2P信息检索及其优化策略

本文研究对等计算（P2P）环境中语义丰富的信息检索及其优化策略，提出了P2P信息检索系统（PIRS），实现了P2P环境中语义丰富的信息检索，定义了一套评价PIRS效率的指标体系；明确了决定PIRS效率的关键因素并提出相应的解决策略，包括：基于向量空间模型的节点数据分类管理策略、基于节点聚类的系统数据管理策略以及自适应查询路由策略，并用实验结果验证了这些策略的有效性。     

P2P信息检索的技术挑战及评价体系

研究对等计算(P2P)信息检索面临的技术挑战及评价体系.重点分析了这类新型信息检索系统亟待解决的技术难题,包括:体系结构、资源定位与查询路由策略、查询结果排序策略与合并机制,以及检索优化策略等;同时介绍了有效的解决方案或指明进一步研究的方向.提出了评价这些解决策略有效性的方法与指标体系.     

P2P信息检索系统的查询结果排序与合并策略

基于P2P信息检索系统的特性,提出了一种完全分布式的查询结果排序与合并策略.首先分析当前P2P信息检索系统查询结果排序和合并问题的根源;接着提出一种完全分布式的查询结果排序与合并策略,包括元数据管理策略、查询结果的排序与合并的实现;然后用详细的实验证明了该策略的有效性.     

一种新型的P2P信息检索系统性能评估方法

对等计算作为学术界和工业界的关注焦点,其在实践中的重要应用主要是信息资源共享.但随着对等计算信息检索系统的广泛应用,如何对其进行客观公正的评价,确定有效、实用的评估标准已迫在眉睫.于是,在以上趋势背景下,文章经过详细研究分析对等计算的信息共享系统后,指出目前P2P信息检索系统面临的实现机制和关键技术问题.之后,经过认真总结和分析,勾勒出评价系统性能的四项指标体系,提出系统性能评估的CTL定律,这对P2P信息检索系统的评价和开发将具有实际指导意义.同时,在此基础上确定今后对等计算信息检索系统研究工作的重点--关键技术及其相应策略.     

一种基于P2P网络Gnutella模型的查询策略

对等计算（peer-to-peer，P2P）应用于数据共享领域时，如何进行数据的查询是提高系统效率、增强系统可扩展性的很重要的技术问题。详细介绍应用在非结构化数据共享系统中的主要查询策略的同时分析了这些策略存在的弊端，并在此基础上提出了一种新的查询策略BDBFS（Better DirectedBreadth-firstTraversal），通过与其它查询方法对比证明该方法可以有效地提高非结构化数据共享系统的效率及可扩展性。     

一种混合式P2P文件共享与检索模型

文件共享是当今对等网络应用的主要方面,本文通过对对等网络中信息共享规律的研究,提出一个基于用户兴趣相似性组成对等组的系统模型.在用户加入对等网时利用用户提供的共享文档信息将用户进行聚类,然后依据查询回馈信息动态调整网络的拓扑结构,尽可能保持对等组内及对等组间的语义相关性、偏爱一致性.为P2P信息检索研究提供了一些新的思路.     

P2P文件传输中网络资源搜索策略改进

资源搜索和共享是P2P网络中重要的应用,如何进行高效资源的查询是提高系统效率、增强系统可扩展性的很重要的技术问题。文中介绍对等网络的基本特征和一些主要改进查询策略,同时分析了这些策略存在的问题,并在此基础上提出了一种基于资源路由表的缓存策略,最后对此方法进行模拟仿真,证明该策略可以有效地提高非结构化文件传输系统的效率及可扩展性。     

基于兴趣挖掘的纯P2P搜索机制研究与实现

在纯P2P环境下，搜索机制是影响信息检索的关键因素之一。本文提出一种基于兴趣索引表的搜索机制，并在此基础上实现纯P2P信息检索原型系统Isearch。该机制首先利用向量空间模型将文件内容向量化，然后对向量空间进行聚类，得到节点的兴趣度，再计算节点之间的兴趣相似度，在本地建立兴趣索引表。在搜索时，根据兴趣索引表直接将查询请求转发到有相似兴趣的节点。实验结果表明，该机制既不影响查询结果，又能减少访问节点的数量，提高查询效率。     

PeerIS:基于Peer-to-Peer的信息检索系统

介绍了对等计算(peer-to-peer,简称P2P)的特征、潜在优势和应用范围,指出了当前P2P数据共享系统存在仅支持弱语义(甚至缺乏语义)和粗粒度(文件水平)共享等局限性.针对这种现状,提出了基于P2P的信息检索,既可充分发掘P2P技术的潜在优势,克服传统信息检索系统的可伸缩瓶颈等问题,又可实现P2P数据共享系统语义丰富和细粒度的信息检索与共享;并开发出PeerIS:基于P2P的信息检索系统.描述了PeerIS的整体构架与节点的内部结构;重点阐述了PeerIS的通信机制、自配置机制、查询机制以及自适应路由机制等实现关键技术;并用实验证明了PeerIS的优异性.     

基于P2P网络的云资源多维查询算法

在云资源共享服务模式中,为实现云资源的多维度查询,提出一种基于P2P网络的云资源多维查询算法.在结构化对等网络的基础上设计一种分层的云资源网络拓扑结构.首先对云资源的属性和属性值分别进行编码,结合云资源多维发布策略实现了云资源多维查询;然后给出了该算法的查询效率分析和稳定性分析.实验结果表明,该算法能快速高效地实现云资源多维度查询,并且不会随着查询维度数和网络节点数的增加而产生较大的查询时延.     

内容感知存储系统中的两阶段检索策略

随着存储系统规模的不断扩大,如何有效组织、管理和查询存储系统中的资源,成为了研究者必须应对的一个问题。目前存储系统中的查询需求主要来自系统管理员对元数据的查询以及普通用户对关键字内容的查询等两个方面。而内容感知存储系统自身所具备的重复数据删除和块相似性检测能力并没有被用于优化上述查询过程。为了充分利用存储系统感知到的上层语义和底层重复数据块信息,为使用者提供高效、便捷的查询服务,提出了内容感知网络存储系统中的两阶段检索策略。该策略将上层基于元数据和关键字的查询与底层存储系统的块相似性查询相结合,利用两次查询相关度的加权平均值作为相似度评价指标。最终的实验结果表明了该策略在降低失效性、提高查全率等方面的有效性。     

Routing Queries through a Peer-to-Peer InfoBeacons Network Using Information Retrieval Techniques

In the InfoBeacons system, a peer-to-peer network of beacons cooperates to route queries to the best information sources. Many internet sources are unwilling to provide more cooperation than simple searching to aid in the query routing.We adapt techniques from information retrieval to deal with this lack of cooperation. In particular, beacons determine how to route queries based on information cached from sources’ responses to queries. In this paper, we examine alternative architectures for routing queries between beacons and to data sources. We also examine how to improve the routing by probing sources in an informed way to learn about their content. Results of experiments using a beacon network to search 2,500 information sources demonstrates the effectiveness of our system; for example, our techniques require contacting up to 71 percent fewer sources than existing peer-to-peer random walk techniques.     

Popularity-aware prefetch in P2P range caching

Unstructured peer-to-peer infrastructure has been widely employed to support large-scale distributed applications. Many of these applications, such as location-based services and multimedia content distribution, require the support of range selection queries. Under the widely-adopted query shipping protocols, the cost of query processing is affected by the number of result copies or replicas in the system. Since range queries can return results that include poorly-replicated data items, the cost of these queries is usually dominated by the retrieval cost of these data items. In this work, we propose a popularity-aware prefetch-based approach that can effectively facilitate the caching of poorly-replicated data items that are potentially requested in subsequent range queries, resulting in substantial cost savings. We prove that the performance of retrieving poorly-replicated data items is guaranteed to improve under an increasing query load. Extensive experiments show that the overall range query processing cost decreases significantly under various query load settings.     

User-private information retrieval based on a peer-to-peer community

Private information retrieval (PIR) is normally modeled as a game between two players: a user and a database. The user wants to retrieve some item from the database without the latter learning which item is retrieved. Most current PIR protocols are ill-suited to provide PIR from a search engine or large database: (i) their computational complexity is linear in the size of the database; (ii) they assume active cooperation by the database server in the PIR protocol. If the database cannot be assumed to cooperate, a peer-to-peer (P2P) user community is a natural alternative to achieve some query anonymity: a user gets her queries submitted on her behalf by other users in the P2P community. In this way, the database still learns which item is being retrieved, but it cannot obtain the real query histories of users, which become diffused among the peer users. We name this relaxation of PIR user-private information retrieval (UPIR). A peer-to-peer UPIR system is described in this paper which relies on an underlying combinatorial structure to reduce the required key material and increase availability. Extensive simulation results are reported and a distributed key management version of the system is described.     

Note segmentation and quantization for music information retrieval

Much research in music information retrieval has focused on query-by-humming systems, which search melodic databases using sung queries. The database retrieval aspect of such systems has received considerable attention, but query processing and the melodic representation have not been examined as carefully. Common methods for query processing are based on musical intuition and historical momentum rather than specific performance criteria; existing systems often employ rudimentary note segmentation or coarse quantization of note estimates. In this work, we examine several alternative query processing methods as well as quantized melodic representations. One common difficulty with designing query-by-humming systems is the coupling between system components. We address this issue by measuring the performance of the query processing system both in isolation and coupled with a retrieval system. We first measure the segmentation performance of several note estimators. We then compute the retrieval accuracy of an experimental query-by-humming system that uses the various note estimators along with varying degrees of pitch and duration quantization. The results show that more advanced query processing can improve both segmentation performance and retrieval performance, although the best segmentation performance does not necessarily yield the best retrieval performance. Further, coarsely quantizing the melodic representation generally degrades retrieval accuracy.     

改进的非结构化P2P网络搜索算法

如何高效地搜索资源是P2P网络中最为关键的问题.非结构化的对等网络,一般以广播方式作为其搜索的基本策略,引发较大的网络流量.针对以上问题,提出了一种利用节点积累的经验指导节点传播查询的路由搜索算法.在该算法中,通过记录节点关注的主题、主题的信息量大小和满足主题的目标节点,并建立对应关系表.当节点收到查询后,就利用该表来指导节点选择查询,以便更快地找到查询结果.仿真结果表明,该算法有效地减少了查询带来的网络流量,提高了查找的成功率.     

Design of a virtual database

This paper proposes a database management system that automatically executes and integrates data retrieval, information deduction and information processing for query processing. The major thesis is that a user should be allowed to define and access any information related to a database—even if the information is not explicitly stored in the database; furthermore, this process of generating new information should be automated in a sense that users do not have to write procedural programs. Thus, the notion of data independence and query processing can be maintained.     

基于MPEG-7的视频语义检索系统

设计和实现一个支持语义的分布式视频检索系统:"语寻"。该系统利用一个改进的视频语义处理工具(该工具基于IBM VideoAnnEx标注工具,并增加镜头语义图标注和自然语言处理的功能)对视频进行语义分析和标注,生成包含语义信息的MPEG-7描述文件,然后对视频的MPEG-7描述文件建立分布式索引,并同时分布式存储视频文件;系统提供丰富的Web查询接口,包括关键字语义扩展查询,语义图查询以及自然语句查询,当用户提交语义查询意图后,便能够迅速地检索到感兴趣的视频和片段,并且可以浏览点播;整个系统采用分布式架构,具备良好的可扩展性,并能够支持海量视频信息的索引和检索。