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1.
从范式优化、索引优化、及查询优化探讨数据库优化设计的方法。在逻辑设计阶段,根据范式优化的要求设计数据库逻辑结构,权衡利弊选出折衷的方案;在数据库物理设计阶段,根据索引优化中的要求在有关属性或属性的组合上建立索引,以优化数据库物理结构;在数据库查询阶段,优化数据查询语句,提高SQL语句的执行效率。  相似文献   

2.
从范式优化、索引优化和查询优化几个方面对数据库的优化设计方法进行分析探讨。在逻辑设计阶段,要按照范式优化的具体要求来设计数据库逻辑结构,比较其优劣从而选择更好的方案;在数据库物理设计阶段,在有关属性或属性的组合上建立索引时要根据索引优化中的具体要求来进行,使数据库物理结构得以优化;在数据库查询阶段,优化数据查询语句,以提高SQL语句的执行效率。  相似文献   

3.
本文从数据库的物理优化、代数优化和规则优化等不同角度,探讨了数据库查询的优化策略,提出了一些查询优化的具体方法.  相似文献   

4.
本文从数据库的物理优化、代数优化和规则优化等不同角度,探讨了数据库查询的优化策略,提出了一些查询优化的具体方法。  相似文献   

5.
分析Java对象持久化层数据检索策略中内存浪费的原因,提出采用查询缓存和集合过滤的方法进行查询优化,降低了访问数据库的频率且避免了在教据查询检索过程中加载不需要的Java对象,从而降低了内存消耗.通过查询电子商务系统中客户的订单记录试验验证了优化方式的有效性.  相似文献   

6.
P2P数据管理   总被引:14,自引:1,他引:14  
余敏  李战怀  张龙波 《软件学报》2006,17(8):1717-1730
P2P(peer-to-peer)技术是未来重构分布式体系结构的关键技术,拥有广阔的应用前景.P2P系统的大多数问题都可归结为数据放置和检索问题,因此,P2P数据管理成为数据库领域活跃的研究课题.当前,P2P数据管理主要有信息检索、数据库查询和连续查询3个子领域,取得了许多研究成果.在介绍P2P技术的优点后,指出了P2P数据管理研究的目标.然后针对上述3个方面,论述P2P数据管理研究的现状,着重讨论了P2P数据库查询的索引构造策略、语义异构的解决方法、查询语义、查询处理策略、查询类型和查询优化技术.通过比较,指出了现状与目标的差距,提出了需要进一步研究的问题.  相似文献   

7.
随着互联网技术的不断发展,使在线资源变得丰富而便于查询.对于科研工作者来说,在线免费检索化合物结构与活性变得更方便快捷.本文介绍了几个常用的化合物活性数据库.并对其站点,内容,检索方式以及各自特点等做了简要阐述.其中PubChem、ChemBank和ChEBI是关于小分子生物活性的公共数据库,eMolecules和ChemExper是关于商购化合物的数据库,他们的检索方式主要有文本检索和结构检索.DrugBank是1个包含药物的结构、药效、作用靶标等信息的综合数据库,有ChemQruery,TextQuery、SeqSearch和Data Extractor,4种检索形式.ZINC数据库是1个免费的用于虚拟筛选的化合物数据库,主要进行化合物结构检索.ADME/Tox Boxes和Molinspiration Cheminformatics是对分子性质进行计算和预测的数据库,用户可以通过分子结构的输入或SMILES进行检索.  相似文献   

8.
工程化学数据库(ECDB)中,分子结构信息的存储、子结构检索和图形显示查询结果是实现结构数据库功能的基础.本文就研究这三问题,在数据存储方面设计了按MOL文件结构的特殊存储方法,压缩大量存储;在子结构检索方面,改进VF2算法的效率;开发图形显示模块,设计子结构检索平台.  相似文献   

9.
本文采用 Kohoenmap自组织神经网络技术 ,提出一种依据检索特征对图像数据库进行预分类的方法 .在文中利用这种预分类实现按类别浏览图像数据库 (image browsing by category)的功能 ,提出一种层次化的类 SS- tree的二分索引结构 .实现建立在预分类基础上的示例查询 .这种查询方法与穷搜索方法相比 ,具有更高的检索效率 ,检索次数随着库规模的增加不会显著增多 .基于图像库的实验验证了分类算法和检索算法的有效性  相似文献   

10.
马捷  李岩  董学敏 《计算机工程》2010,36(13):48-50,53
基于可伸缩矢量图形空间信息表达模型和合理的数据库结构,提出空间索引算法优化选择策略。结合设计模式思想,设计高内聚、低耦合的空间数据索引系统。该系统具有并行建立空间索引的能力,能实现异构XML-enabled空间数据库并行查询。实验结果证明,其检索效率比普通SQL查询高约66%。  相似文献   

11.
Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.  相似文献   

12.
European Community policy and the market   总被引:1,自引:0,他引:1  
Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.  相似文献   

13.
融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。  相似文献   

14.
Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.  相似文献   

15.
This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.  相似文献   

16.
Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008  相似文献   

17.
《计算机科学》2007,34(4):148-148
Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.  相似文献   

18.
为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.  相似文献   

19.
正The 34th Chinese Control Conference and SICE Annual Conference 2015(CCCSICE2015)is organized by the Technical Committee on Control Theory(TCCT)of Chinese Association of Automation(CAA)and the Society of Instrument and Control Engineers(SICE)of Japan,and locally organized by Hangzhou Dianzi University(HDU).  相似文献   

20.
Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.  相似文献   

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