期刊文献+
共找到678篇文章
< 1 2 34 >
每页显示 20 50 100
Semantic-based query processing for relational data integration 被引量:1
1
作者 苗壮 张亚非 +2 位作者 王进鹏 陆建江 周波 《Journal of Southeast University(English Edition)》 EI CAS 2011年第1期22-25,共4页
To solve the query processing correctness problem for semantic-based relational data integration,the semantics of SAPRQL(simple protocol and RDF query language) queries is defined.In the course of query rewriting,al... To solve the query processing correctness problem for semantic-based relational data integration,the semantics of SAPRQL(simple protocol and RDF query language) queries is defined.In the course of query rewriting,all relative tables are found and decomposed into minimal connectable units.Minimal connectable units are joined according to semantic queries to produce the semantically correct query plans.Algorithms for query rewriting and transforming are presented.Computational complexity of the algorithms is discussed.Under the worst case,the query decomposing algorithm can be finished in O(n2) time and the query rewriting algorithm requires O(nm) time.And the performance of the algorithms is verified by experiments,and experimental results show that when the length of query is less than 8,the query processing algorithms can provide satisfactory performance. 展开更多
关键词 data integration relational database simple protocol and RDF query language(SPARQL) minimal connectable unit query processing
下载PDF
Processing Constrained K Closest Pairs Query in Spatial Databases 被引量:1
2
作者 LIU Xiaofeng LIU Yunsheng XIAO Yingyuan 《Wuhan University Journal of Natural Sciences》 EI CAS 2006年第3期543-546,共4页
In this paper, constrained K closest pairs query is introduced, wbich retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R trees in spatial databases, thr... In this paper, constrained K closest pairs query is introduced, wbich retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R trees in spatial databases, three algorithms are presented for answering this kind of query. Among of them, two-phase Range+Join and Join+Range algorithms adopt the strategy that changes the execution order of range and closest pairs queries, and constrained heap-based algorithm utilizes extended distance functions to prune search space and minimize the pruning distance. Experimental results show that constrained heap-base algorithm has better applicability and performance than two-phase algorithms. 展开更多
关键词 spatial databases query processing R-TREE closest pairs query constrained closest pairs query
下载PDF
A method for improving graph queries processing using positional inverted index (P.I.I) idea in search engines and parallelization techniques 被引量:2
3
作者 Hamed Dinari Hassan Naderi 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第1期150-159,共10页
The idea of positional inverted index is exploited for indexing of graph database. The main idea is the use of hashing tables in order to prune a considerable portion of graph database that cannot contain the answer s... The idea of positional inverted index is exploited for indexing of graph database. The main idea is the use of hashing tables in order to prune a considerable portion of graph database that cannot contain the answer set. These tables are implemented using column-based techniques and are used to store graphs of database, frequent sub-graphs and the neighborhood of nodes. In order to exact checking of remaining graphs, the vertex invariant is used for isomorphism test which can be parallel implemented. The results of evaluation indicate that proposed method outperforms existing methods. 展开更多
关键词 graph query processing frequent subgraph graph mining data mining positional inverted index
下载PDF
Privacy-Preserving Multi-Keyword Fuzzy Adjacency Search Strategy for Encrypted Graph in Cloud Environment
4
作者 Bin Wu Xianyi Chen +5 位作者 Jinzhou Huang Caicai Zhang Jing Wang Jing Yu Zhiqiang Zhao Zhuolin Mei 《Computers, Materials & Continua》 SCIE EI 2024年第3期3177-3194,共18页
In a cloud environment,outsourced graph data is widely used in companies,enterprises,medical institutions,and so on.Data owners and users can save costs and improve efficiency by storing large amounts of graph data on... In a cloud environment,outsourced graph data is widely used in companies,enterprises,medical institutions,and so on.Data owners and users can save costs and improve efficiency by storing large amounts of graph data on cloud servers.Servers on cloud platforms usually have some subjective or objective attacks,which make the outsourced graph data in an insecure state.The issue of privacy data protection has become an important obstacle to data sharing and usage.How to query outsourcing graph data safely and effectively has become the focus of research.Adjacency query is a basic and frequently used operation in graph,and it will effectively promote the query range and query ability if multi-keyword fuzzy search can be supported at the same time.This work proposes to protect the privacy information of outsourcing graph data by encryption,mainly studies the problem of multi-keyword fuzzy adjacency query,and puts forward a solution.In our scheme,we use the Bloom filter and encryption mechanism to build a secure index and query token,and adjacency queries are implemented through indexes and query tokens on the cloud server.Our proposed scheme is proved by formal analysis,and the performance and effectiveness of the scheme are illustrated by experimental analysis.The research results of this work will provide solid theoretical and technical support for the further popularization and application of encrypted graph data processing technology. 展开更多
关键词 PRIVACY-PRESERVING adjacency query multi-keyword fuzzy search encrypted graph
下载PDF
Learned Distributed Query Optimizer:Architecture and Challenges
5
作者 GAO Jun HAN Yinjun +2 位作者 LIN Yang MIAO Hao XU Mo 《ZTE Communications》 2024年第2期49-54,共6页
The query processing in distributed database management systems(DBMS)faces more challenges,such as more operators,and more factors in cost models and meta-data,than that in a single-node DMBS,in which query optimizati... The query processing in distributed database management systems(DBMS)faces more challenges,such as more operators,and more factors in cost models and meta-data,than that in a single-node DMBS,in which query optimization is already an NP-hard problem.Learned query optimizers(mainly in the single-node DBMS)receive attention due to its capability to capture data distributions and flexible ways to avoid hard-craft rules in refinement and adaptation to new hardware.In this paper,we focus on extensions of learned query optimizers to distributed DBMSs.Specifically,we propose one possible but general architecture of the learned query optimizer in the distributed context and highlight differences from the learned optimizer in the single-node ones.In addition,we discuss the challenges and possible solutions. 展开更多
关键词 distributed query processing query optimization learned query optimizer
下载PDF
Storage optimization for query processing over data streams
6
作者 唐向红 《Journal of Chongqing University》 CAS 2010年第2期79-92,共14页
A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patte... A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patterns of continuous queries,suitable data structures bring great query processing efficiency.In this paper,we proposed a data structure suitable for weak nonmonotonic update pattern in which the lifetime of each tuple is known at generation time,but the length of lifetime is not necessarily the same.The new data structure combined the ladder queue with the feature of weak non-monotonic update pattern.The experiment results show that the new data structure performs much better than the traditional calendar queue in many cases. 展开更多
关键词 calendar queue ladder queue query processing sliding windows
下载PDF
Efficient Pr-Skyline Query Processing and Optimization in Wireless Sensor Networks
7
作者 Jianzhong Li Shuguang Xiong 《Wireless Sensor Network》 2010年第11期838-849,共12页
As one of the commonly used queries in modern databases, skyline query has received extensive attention from database research community. The uncertainty of the data in wireless sensor networks makes the corresponding... As one of the commonly used queries in modern databases, skyline query has received extensive attention from database research community. The uncertainty of the data in wireless sensor networks makes the corresponding skyline uncertain and not unique. This paper investigates the Pr-Skyline problem, i.e., how to compute the skyline with the highest existence probability in a computational and energy-efficient way. We formulate the problem and prove that it is NP-Complete and cannot be approximated in a given expression. However, the proposed algorithm SKY-SEARCH with pruning techniques can guarantee the computational efficiency given relatively large input size, while the filter-based distributed optimization strategy significantly reduces the transmission cost and the required storage space of the sensor nodes. Extensive experiments verify the efficiency and scalability of SKY-SEARCH and the distributed optimizing strategy. 展开更多
关键词 Wireless Sensor Network query processing UNCERTAIN DATA PROBABILISTIC DATA SKYLINE query
下载PDF
Large Language Model Based Semantic Parsing for Intelligent Database Query Engine
8
作者 Zhizhong Wu 《Journal of Computer and Communications》 2024年第10期1-13,共13页
With the rapid development of artificial intelligence, large language models (LLMs) have demonstrated remarkable capabilities in natural language understanding and generation. These models have great potential to enha... With the rapid development of artificial intelligence, large language models (LLMs) have demonstrated remarkable capabilities in natural language understanding and generation. These models have great potential to enhance database query systems, enabling more intuitive and semantic query mechanisms. Our model leverages LLM’s deep learning architecture to interpret and process natural language queries and translate them into accurate database queries. The system integrates an LLM-powered semantic parser that translates user input into structured queries that can be understood by the database management system. First, the user query is pre-processed, the text is normalized, and the ambiguity is removed. This is followed by semantic parsing, where the LLM interprets the pre-processed text and identifies key entities and relationships. This is followed by query generation, which converts the parsed information into a structured query format and tailors it to the target database schema. Finally, there is query execution and feedback, where the resulting query is executed on the database and the results are returned to the user. The system also provides feedback mechanisms to improve and optimize future query interpretations. By using advanced LLMs for model implementation and fine-tuning on diverse datasets, the experimental results show that the proposed method significantly improves the accuracy and usability of database queries, making data retrieval easy for users without specialized knowledge. 展开更多
关键词 Semantic query Large Language Models Intelligent Database Natural Language processing
下载PDF
Distributed location-based query processing on large volumes of moving items
9
作者 JEON Se gil LEE Chung woo +2 位作者 NAH Yunmook KIM Moon hae HAN Ki joon 《重庆邮电学院学报(自然科学版)》 2004年第5期101-107,共7页
Recently, new techniques to efficiently manage current and past location information of moving objects have received significant interests in the area of moving object databases and location based service systems. In ... Recently, new techniques to efficiently manage current and past location information of moving objects have received significant interests in the area of moving object databases and location based service systems. In this paper, we exploit query processing schemes for location management systems, which consist of multiple data processing nodes to handle massive volume of moving objects such as cellular phone users. To show the usefulness of the proposed schemes, some experimental results showing performance factors regarding distributed query processing are explained. In our experiments, we use two kinds of data set: one is generated by the extended GSTD simulator and another is generated by the real time data generator which generates location sensing reports of various types of users having different movement patterns. 展开更多
关键词 TMO 定位数据服务 GALIS 基础定位处理
下载PDF
Optimizing Query Results Integration Process Using an Extended Fuzzy C-Means Algorithm
10
作者 Naoual Mouhni Abderrafiaa Elkalay Mohamed Chakraoui 《Journal of Software Engineering and Applications》 2014年第5期354-359,共6页
Cleaning duplicate data is a major problem that persists even though many works have been done to solve it, due to the exponential growth of data amount treated and the necessity to use scalable and speed algorithms. ... Cleaning duplicate data is a major problem that persists even though many works have been done to solve it, due to the exponential growth of data amount treated and the necessity to use scalable and speed algorithms. This problem depends on the type and quality of data, and differs according to the volume of data set manipulated. In this paper we are going to introduce a novel framework based on extended fuzzy C-means algorithm by using topic ontology. This work aims to improve the OLAP querying process over heterogeneous data warehouses that contain big data sets, by improving query results integration, eliminating redundancies by using the extended classification algorithm, and measuring the loss of information. 展开更多
关键词 Clustering Classification and Association RULES DATABASE Integration Data WAREHOUSE and REPOSITORY Heterogeneous DATABASES query processing
下载PDF
Research on Fuzzy Matching Query Algorithm Based on Spatial Multi-keyword
11
作者 Suzhi Zhang Yanan Zhao Rui Yang 《国际计算机前沿大会会议论文集》 2017年第1期31-32,共2页
With the rapid growth of spatial data,POI(Point of Interest)is becoming ever more intensive,and the text description of each spatial point is also gradually increasing.The traditional query method can only address the... With the rapid growth of spatial data,POI(Point of Interest)is becoming ever more intensive,and the text description of each spatial point is also gradually increasing.The traditional query method can only address the problem that the text description is less and single keyword query.In view of this situation,the paper proposes an approximate matching algorithm to support spatial multi-keyword.The fuzzy matching algorithm is integrated into this algorithm,which not only supports multiple POI queries,but also supports fault tolerance of the query keywords.The simulation results demonstrate that the proposed algorithm can improve the accuracy and efficiency of query. 展开更多
关键词 SPATIAL data multi-keyword search APPROXIMATE query algorithm RB-tree
下载PDF
Research on Welding Quality Traceability Model of Offshore Platform Block Construction Process
12
作者 Jinghua Li Wenhao Yin +1 位作者 Boxin Yang Qinghua Zhou 《Computer Modeling in Engineering & Sciences》 SCIE EI 2023年第1期699-730,共32页
Quality traceability plays an essential role in assembling and welding offshore platform blocks.The improvement of the welding quality traceability system is conducive to improving the durability of the offshore platf... Quality traceability plays an essential role in assembling and welding offshore platform blocks.The improvement of the welding quality traceability system is conducive to improving the durability of the offshore platform and the process level of the offshore industry.Currently,qualitymanagement remains in the era of primary information,and there is a lack of effective tracking and recording of welding quality data.When welding defects are encountered,it is difficult to rapidly and accurately determine the root cause of the problem from various complexities and scattered quality data.In this paper,a composite welding quality traceability model for offshore platform block construction process is proposed,it contains the quality early-warning method based on long short-term memory and quality data backtracking query optimization algorithm.By fulfilling the training of the early-warning model and the implementation of the query optimization algorithm,the quality traceability model has the ability to assist enterprises in realizing the rapid identification and positioning of quality problems.Furthermore,the model and the quality traceability algorithm are checked by cases in actual working conditions.Verification analyses suggest that the proposed early-warningmodel for welding quality and the algorithmfor optimizing backtracking requests are effective and can be applied to the actual construction process. 展开更多
关键词 Quality traceability model block construction process welding quality management long short-term memory quality data backtracking query optimization algorithm
下载PDF
面向云边端协同的多模态数据建模技术及其应用 被引量:1
13
作者 崔双双 吴限 +1 位作者 王宏志 吴昊 《软件学报》 EI CSCD 北大核心 2024年第3期1154-1172,共19页
云边端协同架构中数据类型多样,各级存储资源与计算资源存在差异,给数据管理带来新的挑战.现有数据模型或者数据模型的简单叠加,都难以同时满足云边端中多模态数据管理和协同管理需求.因此,研究面向云边端协同的多模态数据建模技术成为... 云边端协同架构中数据类型多样,各级存储资源与计算资源存在差异,给数据管理带来新的挑战.现有数据模型或者数据模型的简单叠加,都难以同时满足云边端中多模态数据管理和协同管理需求.因此,研究面向云边端协同的多模态数据建模技术成为重要问题.其核心在于,如何高效地从云边端三层架构中得到满足应用所需的查询结果.从云边端三层数据的数据类型出发,提出了面向云边端协同的多模态数据建模技术,给出了基于元组的多模态数据模型定义,设计了6种基类,解决多模态数据统一表征困难的问题;提出了云边端协同查询的基本数据操作体系,以满足云边端业务场景的查询需求;给出了多模态数据模型的完整性约束,为查询优化奠定了理论基础.最后,给出了面向云边端协同多模态数据模型的示范应用,并从数据存储时间、存储空间和查询时间这3个方面对所提出的数据模型存储方法进行了验证.实验结果表明,所提方案能够有效地表示云边端协同架构中的多模态数据. 展开更多
关键词 多模态数据模型 云边端协同 查询处理
下载PDF
GPU数据库实现技术发展演进
14
作者 刘鹏 陈红 +1 位作者 张延松 李翠平 《计算机学报》 EI CAS CSCD 北大核心 2024年第11期2691-2724,共34页
爆炸式增长的数据对存储和处理数据提出了更高的需求,GPU数据库作为新硬件数据库的一个重要分支,在大容量和高性能处理方面有其独特的优势.GPU数据库作为高性能数据库的代表,在最近几年受到学术界和产业界的关注,一批具有代表性的研究... 爆炸式增长的数据对存储和处理数据提出了更高的需求,GPU数据库作为新硬件数据库的一个重要分支,在大容量和高性能处理方面有其独特的优势.GPU数据库作为高性能数据库的代表,在最近几年受到学术界和产业界的关注,一批具有代表性的研究成果和标志性的实际产品已经出现.GPU数据库的技术发展按照GPU加速型和GPU内存型两种技术路线展开.两种技术路线都有相应的原型系统或产品出现.虽然两种GPU数据库的发展路线在实现上有所不同,但GPU数据库最基本的功能部分和核心技术是相似的,都有查询编译、查询优化、查询执行以及存储管理等功能.当前主流的数据传输方案除了PCIe之外,NVLink、RDMA和CXL等传输方案也为不同处理器之间的数据传输提供了更多的可能性.大多数GPU数据库使用列存储模型来存储数据,少数GPU数据库(如PG-Strom)对两种存储模型都支持.在列存储模型上利用压缩技术能减少数据的存储空间和传输时延.在GPU数据库上进行的压缩和解压的时间应该在整个数据处理的过程中占比很少.在GPU数据库上建立和维护索引不应该有很大的系统开销.JIT编译时间短、编译效率高,是GPU数据库编译的主流.操作符对数据库查询性能的影响非常明显,连接操作、分组聚集和OLAP运算符是目前研究最多的三个类型.目前大多数的研究中,连接和分组聚集算子通常结合在一起研究.在连接算子执行的过程中还和表的连接顺序结合在一起进行考虑.OLAP算子是GPU数据库中的又一个被大量研究的算子,GPU数据库在OLAP算子和模型方面持续受到研究者的关注.GPU数据库有三种查询处理模型,即行处理、列处理和向量化处理.向量化处理和列处理在实际系统中应用较多.由于GPU加速型数据库技术的发展,CPU-GPU协同处理模型上的查询方案与查询引擎也有一定数量的研究成果出现.当前GPU数据库的查询优化研究主要有三部分:多表连接顺序、查询重写和代价模型.然而,GPU数据库的代价评估模型在目前还没有很好的解决方案,GPU数据库的查询优化在未来仍有很大的研究空间.事务在GPU数据库中没有得到很好的研究,尽管有单独的原型系统,但目前的研究还没有取得重大进展.本文总结了GPU数据库各种关键技术已有的研究成果,指出GPU数据库当前存在的问题和面临的挑战,对未来的研究方向进行了展望. 展开更多
关键词 GPU数据库 数据压缩 算子优化 OLAP查询 查询处理
下载PDF
基于大语言模型的数据查询机器人在医学领域的应用
15
作者 全筱筱 熊文举 +1 位作者 潘军杰 曾华堂 《医学新知》 CAS 2024年第9期1057-1063,共7页
本研究对大语言模型(large language model,LLM)、数据查询机器人(data query robot,DQR)的发展历程和研究现状进行了介绍,同时通过实证分析,探讨了在数字医学领域中,基于LLM的DQR的实际应用效果及其在处理医疗数据查询和分析的复杂任... 本研究对大语言模型(large language model,LLM)、数据查询机器人(data query robot,DQR)的发展历程和研究现状进行了介绍,同时通过实证分析,探讨了在数字医学领域中,基于LLM的DQR的实际应用效果及其在处理医疗数据查询和分析的复杂任务中的作用,证实了基于LLM的DQR能为非技术人员提供一个直观且便捷的工具,显著提升医疗数据的查询效率和分析能力。此外,本文还探讨了LLM和DQR技术在当前应用中的局限性及未来发展潜力,为进一步的研究和应用提供参考。 展开更多
关键词 大语言模型 数据查询机器人 数字医学 自然语言处理 深度学习
下载PDF
Apache Flink复杂事件处理语言的形式语义 被引量:1
16
作者 傅宣登 吴志林 《软件学报》 EI CSCD 北大核心 2024年第10期4510-4532,共23页
Apache Flink是目前最流行的流式计算平台之一,已经在工业界得到了广泛应用.复杂事件处理是流式计算的一种重要使用场景,Apache Flink平台定义并实现了一种复杂事件处理语言(简称FlinkCEP).FlinkCEP语法特性丰富,不仅包括常见的过滤、... Apache Flink是目前最流行的流式计算平台之一,已经在工业界得到了广泛应用.复杂事件处理是流式计算的一种重要使用场景,Apache Flink平台定义并实现了一种复杂事件处理语言(简称FlinkCEP).FlinkCEP语法特性丰富,不仅包括常见的过滤、连接、循环等操作,还包括迭代条件、匹配筛选策略等高级特性.FlinkCEP语义复杂,尚缺乏语言规范对其语义进行准确描述,只能通过实现细节来理解,因此对其语义进行形式描述对于开发人员准确理解其语义非常必要.针对FlinkCEP提出一种数据流转换器的自动机模型,该模型包括用于刻画迭代条件的数据变量、存储输出结果的数据流变量、用于刻画匹配筛选策略的迁移优先级等特性.使用数据流转换器对FlinkCEP的语义进行形式建模,并且根据形式语义设计FlinkCEP的查询求值算法,实现原型系统.进一步,生成能够较为全面覆盖FlinkCEP语法特性的测试用例集,利用这些测试用例与FlinkCEP在Flink平台上的实际运行结果进行对比实验.实验结果表明所提出的形式语义与FlinkCEP在Flink平台上的实际语义基本是一致的.而且,对实验结果不一致的情况进行分析,指出FlinkCEP在Flink平台上的实现对于组模式的处理可能存在错误. 展开更多
关键词 流式计算 Flink 复杂事件处理 形式语义 数据流转换器 查询求值
下载PDF
支持混合事务和分析处理的数据库管理系统综述
17
作者 王嵩立 荆一楠 +2 位作者 何震瀛 张凯 王晓阳 《软件学报》 EI CSCD 北大核心 2024年第1期405-429,共25页
数据库管理系统根据应用场景分为事务型(OLTP)系统和分析型(OLAP)系统.随着实时数据分析需求增长,OLTP任务和OLAP任务混合的场景越来越普遍,业界开始重视支持混合事务和分析处理(HTAP)的数据库管理系统.这种HTAP数据库系统除了需要满足... 数据库管理系统根据应用场景分为事务型(OLTP)系统和分析型(OLAP)系统.随着实时数据分析需求增长,OLTP任务和OLAP任务混合的场景越来越普遍,业界开始重视支持混合事务和分析处理(HTAP)的数据库管理系统.这种HTAP数据库系统除了需要满足高性能的事务处理外,还需要满足实时分析对数据新鲜度的要求.因此,对数据库系统的设计与实现提出了新的挑战.近年来,在工业界和学术界涌现了一批架构多样、技术各异的原型和产品.综述HTAP数据库的背景和发展现状,并且从存储和计算的角度对现阶段的HTAP数据库进行分类.在此基础上,按照从下往上的顺序分别总结HTAP系统在存储和计算方面采用的关键技术.在此框架下介绍各类系统的设计思想、优劣势以及适用的场景.此外,结合HTAP数据库的评测基准和指标,分析各类HTAP数据库的设计与其呈现出的性能与数据新鲜度的关联.最后,结合云计算、人工智能和新硬件技术为HTAP数据库的未来研究和发展提供思路. 展开更多
关键词 数据库系统 混合事务和分析处理 查询处理 数据库存储 存储模型 事务处理
下载PDF
XQuery语言的实现 被引量:4
18
作者 谢荣传 谢铉洋 《安徽大学学报(自然科学版)》 CAS 北大核心 2005年第1期23-26,共4页
首先分析了万维网联合会(W3C)提出的XML查询语言XQuery语言的特点,提出了支持W3C的XQuery语言查询处理引擎的体系结构。简要介绍了基于该体系结构所实现的XQuery处理引擎的词法/语法解析、语法转换、类型检查和分析、赋值计算等四个处... 首先分析了万维网联合会(W3C)提出的XML查询语言XQuery语言的特点,提出了支持W3C的XQuery语言查询处理引擎的体系结构。简要介绍了基于该体系结构所实现的XQuery处理引擎的词法/语法解析、语法转换、类型检查和分析、赋值计算等四个处理阶段涉及的主要内容。 展开更多
关键词 Xquery语言 W3C XML查询 查询处理 体系结构 引擎 万维网 语法 赋值 支持
下载PDF
XML查询语言XQuery的研究与实现 被引量:5
19
作者 华珊珊 谢铉洋 《计算机技术与发展》 2009年第4期48-50,共3页
XQuery是一种对XML结构的文档和数据进行查询的语言。在对该查询语言规范体系分析、理解和研究的基础上,提出了支持W3C的XQuery语言的查询处理引擎的体系结构。针对各个输入输出和处理模块按数据流的方式逐一进行分析,对整个系统的运行... XQuery是一种对XML结构的文档和数据进行查询的语言。在对该查询语言规范体系分析、理解和研究的基础上,提出了支持W3C的XQuery语言的查询处理引擎的体系结构。针对各个输入输出和处理模块按数据流的方式逐一进行分析,对整个系统的运行状态做了一个总体的介绍。按照这个体系结构,一个XQuery查询处理引擎已经被实现。 展开更多
关键词 XML Xquery 查询 处理引擎
下载PDF
基于变分自编码器的近似聚合查询优化方法
20
作者 黄龙森 房俊 +1 位作者 周云亮 郭志城 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第5期931-940,共10页
针对偏态数据分布不平衡,传统近似聚合查询方法难以抽样生成偏态分布数据的问题,提出基于优化的变分自编码器的近似聚合查询方法,研究近似聚合查询方法对偏态分布数据的近似聚合查询准确率的影响.在预处理阶段对偏态分布数据进行分层分... 针对偏态数据分布不平衡,传统近似聚合查询方法难以抽样生成偏态分布数据的问题,提出基于优化的变分自编码器的近似聚合查询方法,研究近似聚合查询方法对偏态分布数据的近似聚合查询准确率的影响.在预处理阶段对偏态分布数据进行分层分组,对变分自编码器生成模型的网络结构和损失函数进行优化,降低近似聚合查询相对误差.实验结果表明,与基准方法相比,近似聚合查询对偏态分布数据的查询相对误差更小,且随着偏态系数的提高,查询相对误差的上升趋势更平缓. 展开更多
关键词 近似查询处理 偏态分布 机器学习 变分自编码器 分组抽样
下载PDF
上一页 1 2 34 下一页 到第
使用帮助 返回顶部