VFP视图技术应用介绍

MicrosoftVisualFoxPro6.0是微软面向对象的程序设计开发工具之一,它在企、事业单位的信息管理系统中发挥了重要作用。 　　视图是从一个表或多个表或其他视图上导出的表。在应用程序设计中,要创建自定义并且可更新的数据集合,我们需要使用视图。视图兼有表和查询的特点：与查询相类似的是,视图可以用来从一个或多个相关联的表或视图中提取有用信息;与表相类似的是,视图可以用来更新其中的信息,并将更新结果永久保存在磁盘上。我们可以用视图使数据暂时从数据库中分离成为游离数据,以便在主系统之外收集和修改数据。在开发中使…     

OODB中基于多个类的视图维护

视图是可以被物化和查询的虚拟数据,是查询模式的一个重要的方面,它在保持数据的统一性和完整性方面有很大的作用。在视图被物化以后,每当数据库中的数据发生变化时,视图也应该更新,否则,就违背了数据的一致性和完整性。本文主要研究利用被修改的数据库对象进行视图维护的简单方法。     

视图技术在大型数据库系统中的应用

１引言 ＭＳ ＳＱＬ Ｓｅｒｖｅｒ是 Ｍａｃｒｏｓｏｆｔ公司开发的大型数据库系统。在大型数据库系统应用中,信息的快速检索和更新起着极为重要的作用,若想为应用系统建立一个查询和修改相结合的数据集,可以使用视图。视图能够从一个或多个相关表中提取数据（查询）,也可以使用视图更新所提取的数据,并将更新后的结果送回到基表中（修改）。在 ＭＳ ＳＱＬ Ｓｅｒｖｅｒ中通过使用视图技术对数据库（表）的数据进行插入、修改、查询、删除等操作,可以使这一大型数据库系统的复杂应用简单化。２视图概念 在数据库管理系统中,用户数据…     

泛化视图及其更新一致性维护问题??

泛化视图是一种新出现的数据发布形式。与经典的物化视图不同,泛化视图中的数据是通过对物化视图中数据进行泛化操作得到的。当基础数据库发生更新操作时,如何对泛化视图进行一致性维护是一个亟待解决的问题。分析了泛化视图在对基础数据库进行插入、删除、修改更新操作时可能出现的更新反应;提出了多维桶的概念,并给出了多维桶的构造方法及相关操作;在此基础上,对于基础数据库的不同更新操作,分别给出了基于多维桶的泛化视图更新一致性算法,解决了泛化视图的更新一致性维护问题。     

CIMS信息集成平台中实例化OO视图的维护方法

为满足ＣＩＭＳ信息集成平台中全局集成级物理集成策略的需求，本文研究了实例化面向对象视图的有效维护问题，提出了一个实例化面向对象视图的有效维护方法，该方法是代数和基于等价推理的，它使用对象代数夜为基本描述语言，本文给出了一个传播基类的更新到实例化ＯＯ视图的更新传播算法，证明了该算法是正确的并保持了一定程度的最小性，即宁可以确保没有不必要的实例被计算，分析和实验结果表明，大多数情况下改变传递算法都比重     

CIMS信息集成平台中实例代OO视图的维护方法

为满足CIMS信息集成平台中全局集成级物理集成策略的需求，本文研究了实例化面向对象视图的有效维护问题，提出了一个实例化面向对象视图的有效维护方法．该方法是代数的和基于等价推理的，它使用对象代数作为基本描述语言．本文给出了一个传播基类的更新到实例化OO视图的更新传播算法，证明了该算法是正确的并保持了一定程度的最小性，即它可以确保没有不必要的实例被计算．分析和实验结果表明，大多数情况下改变传递算法都比重新计算视图有效．     

Visual Foxpro 视图性能优化方法

Cisual FoxPro(以下简称VFP)以其功能强大,面向对象,支持客户机／服务器等诸多优点,已广泛应用于数据库开发领域。在数据库应用中,信息的快速检索和更新起着极为重要的作用。若想为应用建立一个查询和修改相结合的数据集,可以使用视图。视图能够从一个或多个相关表中提取一套数据;也可以使用视图更新所提取的信息并将更新后的结果送回源表或基表中。视图是VFP数据库的一个新特点,有效地使用视图,可以充分发挥VFP的数据访问的高性能特点。但是,并非所有的使用者都能有效地使用VFP的视图技术。相反,往往由于对视图使用不当,     

自适应图学习诱导的子空间聚类

子空间聚类是机器学习领域的热门研究课题。它根据数据的潜在子空间对数据进行聚类。受多视图学习中协同训练算法的启发,提出一个自适应图学习诱导的子空间聚类算法,该算法首先将单视图数据多视图化,再利用不同视图的信息迭代更新图正则化项,得到更能反映聚类性能的块对角关联矩阵,从而更准确地描述数据聚类结果。在四个标准数据集上与其他聚类算法进行对比实验,实验结果显示该方法具有更好的聚类性能。     

基于数据服务的嵌套视图动态更新方法

数据服务屏蔽了数据访问的复杂性,并且支持用户以可视化方式定义装载异构数据源的嵌套视图.然而,当异构数据源输出的数据发生更新时,该更新需要通过数据服务逐层传播到顶层的嵌套视图,一类挑战性问题是,如何减少更新传播过程中的冗余计算,提高嵌套视图的数据新鲜度.为此文中提出了基于数据服务的嵌套视图动态更新方法,该方法利用指针为嵌套视图中的元组建立嵌套任意层次的数据服务的引用,同时给出了一种记录数据服务更新的日志以及在该日志上的嵌套视图增量更新算法.文中在原型系统中实现了该算法并且进行了实验分析,实验结果表明,该方法减少了70％的嵌套视图的更新时间,提高了60％的嵌套视图的数据新鲜度.     

OODB中连接视图的物化和增量保持技术

提出了一个实现OODB中连接视图物化和增量保持的算法，基本思想是扩充了文献[1]中的OODB模型，使其便利于连接视图的物化和增量保持，为每个类中的对象增加一个视图标识，用来标记该对象是否在相应视图中，以减少连接运算，最后，开发出一系列算法来实现由两个类做连接运算生成一视图的物化及保持工作。     

View specification and manipulation for a semantic data model

Semantic data models are increasing in popularity and use, but they are also becoming increasingly complex and difficult to manage. In this paper we extend the definition of a semantic data model to give users the power to specify and manipulate views. Our model supports both high-level object-class views and high-level relationship-set views. To define these views, we extend the traditional method of view definition (through query formulation) to also include view definition by a dominant object class, by an independent object class, and by a relational object class. A set of operators to specify and manipulate views is also defined. These operators allow a user to create and destroy views, implode and explode views, hide and expose semantic-model elements. We also provide algorithms to extract an instance graph for a high-level object in a semantic-model view and to transform a semantic-model view hierarchy into an equivalent atomic model. Implications and applications of views in our model are also discussed.     

Understanding the implications of view update policies

Database views are traditionally described as unmaterialized queries, which may be coincidentally updatable according to some fixed criteria. One of the problems in updating through views lies in determining whether a given view modification can be correctly translated by the system. To define an updatable view, a view designer must be aware of how an update request in the view will be mapped into updates of the underlying relations. Furthermore, because of side effects, the view designer must also be made aware of the effects of isolated updates back into the view.To address this problem, we present a general algorithm that predicts the effects of arbitrary mapping policies. Given an update policy, this algorithm indicates whether a desired update will, in fact, occur in the view and describes all possible side effects it may have, documenting the conditions under which they occur. The algorithm subsumes the results obtained by other view design tools, and generalizes their use to encompass a larger class of views.This work was supported in part by grant A9292 from the Natural Sciences and Engineering Research Council of Canada and by scholarship 200 398/80 from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico-CNPq, Brasil.     

Accumulator-based inexact matching using relational summaries

We are building a system that can rapidly determine the pose of a known object in an unknown view using a view class model of the object. The system inputs a three-dimensional CAD model; converts it to a three-dimensional vision model that contains the surfaces, edges, vertices, and topology of the object; and uses the vision model to determine the view classes or representative views of the object. In this paper we define therelational pyramid structure for describing the features in a particular view or view class of an object and thesummary structure that is used to summarize the relational information in the relational pyramid. We then describe an accumulator-based method for rapidly determining the view class(es) that best match an unknown view of an object.This research was partially supported by the National Aeronatics and Space Administration (NASA) through a subcontract from Machine Vision International.     

对象类视图中蕴涵的依赖关系

本文研究关系模型中对象类视图关系模式的数据依赖问题。关系数据库中用一组表存放一个对象类的数据,并用视频实现对象类。本文分析该视图的列之间存在的函数依赖和多值依赖,并证明了类的所有单值和多值属性组成对象标识的多值依赖基。     

面向三维模型高效观察的视点选择技术综述

高效的模型观察,对提高生产实践工作效率具有重要的意义。为此,视点选择技术在近些年得到了很大的发展,是提高模型观察效果的重要技术之一。文章对视点选择技术进行了较系统的梳理,重点讨论了视点度量技术及其发展现状,并探讨了视点采样技术的发展及视点选择技术在多方面应用的情况。最后,讨论了视点选择技术的发展趋势及其应用前景。     

An Order-Based Theory of Updates for Closed Database Views

The fundamental problem in the design of update strategies for views of database schemata is that of selecting how the view update is to be reflected back to the base schema. This work presents a solution to this problem, based upon the dual philosophies of closed update strategies and order-based database mappings. A closed update strategy is one in which the entire set of updates exhibit natural closure properties, including transitivity and reversibility. The order-based paradigm is a natural one; most database formalisms endow the database states with a natural order structure, under which update by insertion is an increasing operation, and update by deletion is decreasing. Upon augmenting the original constant-complement strategy of Bancilhon and Spyratos – which is an early version of a closed update strategy – with compatible order-based notions, the reflection to the base schema of any update to the view schema which is an insertion, a deletion, or a modification which is realizable as a sequence of insertions and deletions is shown to be unique and independent of the choice of complement. In addition to this uniqueness characterization, the paper also develops a theory which identifies conditions under which a natural, maximal, update strategy exists for a view. This theory is then applied to a ubiquitous example – single-relational schemata constrained by equality-generating dependencies. Within this framework it is shown that for a view defined as a projection of the main relation, the only possibility is that the complement defining the update process is also a projection, and that the reconstruction is based upon functional dependencies.     

Deriving Object Oriented Federated Databases and Processing Federated Queries

In this paper, we present a federated query processing approach to evaluate queries on an Object-Oriented (OO) federated database. This approach has been designed and implemented in the OO-Myriad project, which is an OO extension to the Myriad FDBS researchmyriad:94. Since data integration is performed as part of federated query processing, we have proposed outerjoin, outer-difference and generalized attribute derivation operations together with the traditional relational operations, to be used for integration purposes. To define an OO federated database as a virtual view on multiple OO export databases, we adopt a database mapping strategy that systematically derives each of the class extents, deep class extents and relationships of the federated database using an operator tree consisting of the integration operations. By augmenting federated database queries with this algebraic mapping information, query execution plans can be generated. Based on the original Myriad query processing framework, we have realized the proposed OO federated query processing approach in the OO-Myriad prototype.     

多视角数据缺失补全

随着信息技术的快速发展,现实生活中不断涌现出大量的多视角数据,由此应运而生的多视角学习已成为机器学习领域的研究热点.然而,在数据获取过程中,由于收集的难度、高额成本或设备故障等问题,往往导致收集到的多视角数据出现视角缺失,这使得一些多视角学习方法无法有效进行.为此,本文提出了一种基于视角相容性的多视角数据缺失补全方法.通过监督的共享子空间学习,获得与每类多视角数据相对应的共享子空间,从而建立视角相容性判别模型.与此同时,基于共享子空间重构误差等同分布的假设,提出了针对视角缺失的多视角数据的共享表征获取方法,实现多视角缺失数据的预补全.在此基础上,进一步通过多元线性回归实现缺失视角的精确补全.此外,本文还把所提出的视角补全方法拓展到解决含有噪声的多视角数据的降噪问题.在UCI、COIL-20以及人工合成数据集上的实验结果验证了本文算法的有效性.     

Efficient view selection by measuring proxy information

View selection aims at finding good views that can watch model information as much as possible. However, existing view evaluation methods used to measure model properties are generally complex and very time‐consuming. In this paper, we address this challenge by generating succinct proxy information to measure the view quality. The proxy information is generated by principal component analysis of the model to obtain its six principal viewing directions and consists of the representative information computed by the principal viewing directions. We discuss and validate the effectiveness of the proxy information for view evaluation. Thus, measuring the proxy information for view evaluation, the time complexity can be reduced as it is independent of the facet number of the model. This is superior to existing methods by straight measurement of model properties and provides acceleration for view selection. Experimental results show that we can obtain good views as state‐of‐the‐art methods and speed up view selection by at least two orders of magnitudes and achieve more acceleration when the models have more facets. Copyright © 2016 John Wiley & Sons, Ltd.