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1.
高维数据查询处理技术一直是P2P领域的研究热点.现有方法大都存在维护代价大、查询处理性能不高的问题.提出一种有效支持高维数据KNN查询处理的P2P语义覆盖网络--语义多层环SMR(semantic multi-level ring).SMR能够按照语义信息将数据对象和节点划分成多个语义簇,每个语义簇通过维护近邻索引和远端索引将不同层次环中的语义簇相互连接,形成P2P语义覆盖网络.在SMR中,采用一种高效语义簇编码方法将高维语义空间转换成一维编码空间降低了高维空间维护代价.在此基础上,提出一种高效的KNN查询处理算法.基于真实数据集和合成数据集的实验表明,SMR具有良好的查询处理能力、语义簇划分能力和可扩展性.  相似文献   

2.
P2P语义搜索研究进展   总被引:1,自引:0,他引:1  
P2P语义搜索方法多种多样。首先,制定了一套综述方案,从语义描述方法、覆盖网络结构、查询扩展技术、资源聚类方式以及本体数量等5个角度对现有方法进行综述。然后,选择10种典型语义搜索方法进行分析比较,总结P2P语义搜索的主要特征。最后,指出下一步研究应探索新的资源组织与搜索机制,并着重关注P2P语义搜索性能评价、查询扩展技术完善、搜索结果排序等方面。  相似文献   

3.
本文综述了基于语义的视频检索的研究现状,以帮助未来的研究人员了解基于语义的视频检索领域中可用的技术,视频检索系统的产生是为了在互联网或数据库中的大量视频数据集中找到用户想要查询的视频.本文对基于语义的视频检索过程进行了说明与讨论,本文还对基于语义的视频检索中,解决语义鸿沟这一主要问题的相关技术进行了综述.语义鸿沟的形成是因为从视频内容中提取的低层特征与现实世界中用户对这些特征的认知存在差异,将视频内容的低层特征转化为高层的语义概念是一个备受关注的研究课题.  相似文献   

4.
针对消防领域中传统信息检索技术处理语义能力薄弱的问题,提出一种基于工业消防本体的语义查询方法.该方法将信息检索方式和语义Web技术结合起来,在工业消防本体的基础上,通过构造消防信息的推理规则,并在Jena平台下实现了工业消防领域基于语义的检索和查询功能.实验结果表明:相对于传统的基于关键词的检索方法,基于语义的检索方法能够解决工业消防领域中数据语义异构问题,提高工业消防领域信息检索的查全率和查准率.  相似文献   

5.
P2P是近年来网络研究领域的热点。当前P2P网络的研究多集中在文件共享的应用,其检索机制只支持基于关键词的查询,缺乏对语义检索的支持。本文将语义网技术和P2P的优点结合起来,建立P2P网络的语义检索机制。通过建立基于本体概念的分布式倒排索引,使检索过程不再是关键词的精确匹配,而是通过不同节点本体中的概念之间的语义关系的逻辑推理实现检索请求与文档在语义上的匹配。实验表明,本文提出的结构化P2P网络语义检索方法,比基于关键词精确匹配的检索方法有较高的查全率和查准率。  相似文献   

6.
利用网格技术实现的异构数据源集成环境中,引入本体可以解决网格数据的语义查询问题。为了提高网格环境中语义查询的效率,提出了一个基于本体的语义查询优化器(GSQO),该优化器主要实现了以下3个模块的优化:(1)用户查询语义扩展;(2)资源选择;(3)并行处理。实验结果表明,GSQO通过采取上述优化策略提供了较好的查询效率。  相似文献   

7.
语义网技术的发展为传统的信息集成领域带来了新的契机,构建基于语义的信息集成系统对于知识的表示、信息的组织与检索等有着重要的意义.通过对领域本体的构建方法和对基于本体的数据集成方法的分析,提出一种基于语义的信息集成模型,改进了传统的基于视图的查询响应方法,在传统的数据库层上构建了RDF/OWL视图,实现了关系模式向本体模式的转换,将SPAROL向SQL转化的查询处理运用于查询重写中.从技术与应用的角度论证了系统的可行性.  相似文献   

8.
传统的查询树及基于多重加权树的查询优化方法,研究得比较成熟,语义查询优化方法将一个查询变换成一个或数个语义等价的查询,基于Agent的并行数据库查询优化采用Multi-Agent技术自动查找与给定查询有关的完整性约束条件,使得多个关系间连接操作的效率得到很大地提高.并行数据库的查询优化领域的3个重要方向为基于机群系统的并行数据库查询优化研究,将MAS技术及专家系统引入本领域,将模拟退火算法及神经网络算法引入本领域.  相似文献   

9.
语义检索关键技术研究   总被引:1,自引:1,他引:0  
传统的基于关键字的信息检索,由于忽视了关键词本身所含的语义信息,故只能得到较低的查全率和查准率.而源于知识工程和人工智能领域的本体理论和技术,能够很好地处理自然语言理解问题和具有基于语义的推理机制,因此成为改进传统信息检索方式的良好工具.与传统的检索技术相比,它能提高检索的精度和覆盖率,减少了不相关的返回结果.文中将对语义检索系统中所涉及到的语义检索预处理及查询语义扩展等关键技术进行分析研究,为语义检索系统的顺利实施莫定了良好的理论与实践基础.  相似文献   

10.
语义缓存技术一直以来是数据库研究的热点之一。语义缓存是指将用户向服务器端提交的查询语句和查询实际得到的结果数据同一存储在指定的缓存中,因而其不仅包含有数据,还有对数据的相关描述信息,从而可以提高查询效率。在语义缓存之前,还存在页面缓存、元组缓存、块缓存等缓存技术。文中首先介绍语义缓存的模型,然后阐述和分析语义缓存查询匹配算法和缓存替换策略,最后对语义缓存技术进行总结,从而为语义缓存技术的进一步研究提供一定的理论基础。  相似文献   

11.
The retrieval facilities of most peer-to-peer (P2P) systems are limited to queries based on a unique identifier or a small set of keywords. The techniques used for this purpose are hardly applicable for content based image retrieval (CBIR) in a P2P network. Furthermore, we will argue that the curse of dimensionality and the high communication overhead prevent the adaptation of multidimensional search trees or fast sequential scan techniques for P2P CBIR. In the present paper we will propose two compact data representations that can be distributed in a P2P network and used as the basis for a source selection. This allows for communicating with only a small fraction of all peers during query processing without deteriorating the result quality significantly. We will also present experimental results confirming our approach.  相似文献   

12.
P2P搜索新技术:智能搜索技术   总被引:1,自引:0,他引:1  
沈洁  胡金初 《微机发展》2005,15(11):91-93
在P2P网络中正确高效地搜索信息十分重要,然而现有的搜索技术并不能很好地满足用户要求。文中提出了由历史记录、相似度和站点优先级3部分组成的新的信息搜索技术———智能搜索技术。在智能搜索技术中每个站点都各自记录以往搜索的历史记录,以此结合搜索要求计算出最可能拥有所需结果的站点,最后仅向这些站点发送搜索请求。通过在中间件上的测试,比较了不同信息搜索技术的性能,智能搜索技术能在使用较少搜索消息的情况下得到较高的搜索成功率。  相似文献   

13.
P2P信息检索系统的查询结果排序与合并策略   总被引:3,自引:0,他引:3  
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.  相似文献   

14.
The increasing use of mobile communications has raised many issues of decision support and resource allocation. A crucial problem is how to solve queries of Reverse Nearest Neighbour (RNN). An RNN query returns all objects that consider the query object as their nearest neighbour. Existing methods mostly rely on a centralised base station. However, mobile P2P systems offer many benefits, including self-organisation, fault-tolerance and load-balancing. In this study, we propose and evaluate 3 distinct P2P algorithms focusing on bichromatic RNN queries, in which mobile query peers and static objects of interest are of two different categories, based on a time-out mechanism and a boundary polygon around the mobile query peers. The Brute-Force Search Algorithm provides a naive approach to exploit shared information among peers whereas two other Boundary Search Algorithms filter a number of peers involved in query processing. The algorithms are evaluated in the MiXiM simulation framework with both real and synthetic datasets. The results show the practical feasibility of the P2P approach for solving bichromatic RNN queries for mobile networks.  相似文献   

15.
基于Kademlia的P2P多维范围查询系统   总被引:1,自引:1,他引:0       下载免费PDF全文
结构化P2P网络具有良好的可扩展性,但难以支持多关键词查询、范围查询等复杂查询。该文分析已有复杂查询方法,提出一种基于Kademlia的P2P多维范围查询系统K-net。K-net在进行多维范围查询时,完成高维范围数据降维和范围划分,减少查询所需带宽。模拟结果显示,该系统具有良好的查询准确度和可扩展性。  相似文献   

16.
We consider the problem of efficiently computing distributed geographical k-NN queries in an unstructured peer-to-peer (P2P) system,in which each peer is managed by an individual organization and can only communicate with its logical neighboring peers.Such queries are based on local filter query statistics,and require as less communication cost as possible,which makes it more difficult than the existing distributed k-NN queries.Especially,we hope to reduce candidate peers and degrade communication cost.In this paper,we propose an efficient pruning technique to minimize the number of candidate peers to be processed to answer the k-NN queries.Our approach is especially suitable for continuous k-NN queries when updating peers,including changing ranges of peers,dynamically leaving or joining peers,and updating data in a peer. In addition,simulation results show that the proposed approach outperforms the existing Minimum Bounding Rectangle (MBR.)-based query approaches,especially for continuous queries.  相似文献   

17.
郎皓  王斌  李锦涛  丁凡 《软件学报》2008,19(2):291-300
目前,查询性能预测(predicting query performance,简称PQP)已经被认为是检索系统最重要的功能之一.近几年的研究和实验表明,PQP技术在文本检索领域有着广阔的发展前景和拓展空间.对文本检索中的PQP进行综述,重点论述其主要方法和关键技术.首先介绍了常用的实验语料和评价体系;然后介绍了影响查询性能的各方面因素;之后,按照基于检索前和检索后的分类体系概述了目前主要的PQP方法;简介了PQP在几个方面的应用;最后讨论了PQP所面临的一些挑战.  相似文献   

18.
When a query is posed on a centralized database, if it refers to attributes that are not defined in the database, the user is warranted to get either an error or an empty set. In contrast, when a query is posed on a peer in a P2P system and refers to attributes not found in the local database, the query should not be simply rejected if the relevant information is available at other peers. This paper proposes a query model for unstructured P2P systems to answer such queries. (a) We introduce a class of polymorphic queries, a revision of conjunctive queries by incorporating type variables to accommodate attributes not defined in the local database. (b) We define the semantics of polymorphic queries in terms of horizontal and vertical object expansions, to find attributes and tuples, respectively, missing from the local database. We show that both expansions can be conducted in a uniform framework. (c) We develop a top-K algorithm to approximately answer polymorphic queries. (d) We also provide a method to merge tuples collected from various peers, based on matching keys specified in polymorphic queries. Our experimental study verifies that polymorphic queries are able to find more sensible information than traditional queries supported by P2P systems, and that these queries can be evaluated efficiently.  相似文献   

19.
基于P2P的个性化Web信息检索   总被引:2,自引:0,他引:2  
为了克服Web搜索引擎在可扩展性、协作性和个性化等方面存在的不足,提出了一种基于Peer to Peer 的全分布、协作式、自组织的个性化Web信息检索,定义了以查询主题为中心进行主题聚类、数据组织和查询路由的用户协作共享策略,设计了协作生成用户兴趣列表向量、对相似语义查询进行主题聚类和更新、基于查询集建立倒排索引以及基于查询主题进行语义路由等算法和机制,以提供人性化、协作式、个性化的搜索。模拟实验表明,原型系统可以加快查询速度,减轻网络负荷,提高搜索的准确率。  相似文献   

20.
This paper proposes a two-level P2P caching strategy for Web search queries. The design is suitable for a fully distributed service platform based on managed peer boxes (set-top-box or DSL/cable modem) located at the edge of the network, where both boxes and access bandwidth to those boxes are controlled and managed by an ISP provider. Our solution significantly reduces user query traffic going outside of the ISP provider to get query results from the respective Web search engine. Web users are usually very reactive to worldwide events which cause highly dynamic query traffic patterns leading to load imbalance across peers. Our solution contains a strategy to quickly ease imbalance on peers and spread communication flow among participating peers. Each peer maintains a local result cache used to keep the answers for queries originated in the peer itself and queries for which the peer is responsible for by contacting the Web search engine on-demand. When query traffic is predominantly routed to a few responsible peers our strategy replicates the role of “being responsible for” to neighboring peers so that they can absorb query traffic. This is a fairly slow and adaptive process that we call mid-term load balancing. To achieve a short-term fair distribution of queries we introduce a location cache in each peer which keeps pointers to peers that have already requested the same queries in the recent past. This lets these peers share their query answers with newly requesting peers. This process is fast as these popular queries are usually cached in the first DHT hop of a requesting peer which quickly tends to redistribute load among more and more peers.  相似文献   

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