DOL: 一个演绎对象库语言

演绎对象数据库是对象数据模型和演绎数据库集合的产物.它集成演绎数据库的查询能力和对象数据库的强大建模能力.DOL(deductive object base language)是作者设计的一种演绎对象库语言,它支持类、类层次、继承、集合、部分集、方法及重载和否定.文章着重研究继承、重载和复杂结构化值的交互关系.定义了压缩操作子和重载操作子.基于这两个操作子,定义了与经典逻辑程序类似的直接后承操作子,并研究其不定点性质.     

面向对象数据库系统中的DS-粗糙集及其应用

在面向对象数据库中,将属性和方法封装在一起形成类,类的实例构成对象。对象在方法的作用下,其属性值不断地发生变化,使得对象迁入或迁出集合,则研究的对象集合成为双向DS-集合。分析类与对象中的S-粗集特征,定义了基于动态特征的面向对象DS-粗集。DS-粗集具有类的封装性和隐蔽性特征,DS-粗集是S-粗集和粗集的一般形式,是S-粗集和粗集的进一步推广。最后通过一个简单实例说明了DS-粗集在面向对象数据库系统中的应用基础。     

一类弱支配集问题的近似算法

支配集问题和集合覆盖问题均是图论中的经典问题,尤其是集合覆盖问题,它的近似算法在许多其他问题中均有非常多的应用,如设施选址问题、服务器的安置问题等。本文研究了支配集问题和集合覆盖问题的关系,讨论了几个弱支配集问题和弱覆盖问题、弱集合覆盖问题等,给出完全支配集问题的近似比为Inn的近似算法,分析了弱完全支配集问题的不可近似比最小规模,讨论了集合击中问题和弱集合b-覆盖问题的最小规模,同时讨论了完全支配集问题、集合d-击中等问题的不可近似性。     

基于Realms的空间数据库系统实现技术

Realms是将所有空间元素定义在分辨率确定的网格上的数学模型,它提出所有空间对象共享一个空间元素集合及空间元素的排序规则。Realms可以对空间数据进行离散化和约束,使二维空间线性化为一维有序元素集,基于Realms的空间数据组织能有效地支持平面扫描算法,通过对空间对象的平面扫描高效简单地实现多数空间分析算法。文中阐述了Realms的概念,给出了基于Realms的空间数据库对空间对象的建模,并用扫描线技术实现空间分析算法。     

基于Realms的空间数据库系统实现技术

Realms是将所有空间元素定义在分辨率确定的网格上的数学模型,它提出所有空间对象共享一个空间元素集合及空间元素的排序规则.Realms可以对空间数据进行离散化和约束,使二维空间线性化为一维有序元素集,基于Realms的空间数据组织能有效地支持平面扫描算法,通过对空间对象的平面扫描高效简单地实现多数空间分析算法.文中阐述了Realms的概念,给出了基于Realms的空间数据库对空间对象的建模,并用扫描线技术实现空间分析算法.     

一种开采频繁项目集集合的快速算法

在大的数据集合中,开采其中的频繁项目集集合是数据挖掘中极具挑战的重要任务。已经有很多高效的算法被总结了出来。本文提出了一种思想,即开采频繁项目集集合的一 个子集,我们称之为频繁无析取规则集集合,而并非开采完全的频繁项目集集合。我们证明能借助它不读取数据库而还原出频繁项目集集合的全集和它们的支持度。本文还提 提出了一个开采无析取规则集集合的算法HOPE-Ⅱ,实验结果显示了其高效性。我们将它与另一种称为频繁封闭集的精简集进行对比,几乎所有的实验结果都显示使用无析取规则集集合比使用封闭集集合来开采频繁项目集集合更有效。     

外P-集合副集的τ-生成与τ-强生成

P-集合是由内P-集合与外P-集合构成的集合对,它具有动态特性。在外P-集合的基础上,定义了外P-集合的副集A(X F)、外P-集合副集τ-生成Aτ(X F)与外P-集合副集τ-强生成Aτ?(X F),讨论了三者之间的关系,得到外P-集合副集τ-生成与外P-集合副集τ-强生成关系定理、辨识定理与外P-集合副集的生成定理。对P-集合理论进行了补充。     

集合特征码及相关算法研究

在传统的集合运算过程中,集合内的元素一般通过自然语言表示,而不是形式化表示,这就在计算机处理时影响了集合运算的效率。为了解决这个问题,将二进制引入到集合运算过程中,提出集合特征码的概念,并定义了一系列的集合特征码运算规则,从而形成了一个较为完备的、形式化的集合特征码运算体系。在上述集合特征码的理论体系下,提出一系列的相关算法,从而在算法的层次上实现了集合特征码的理论体系。实验结果表明,通过集合特征码理论及相关算法,集合运算可以通过0、1运算快速实现,并且其成功实现了数据库中的查询操作。     

粗糙形式概念抽取的属性集合幂集方法

为了最大限度地抽取出形式背景中的粗糙形式概念,以便为粗糙概念格的构建提供完整的信息源,对粗糙形式概念的抽取进行了研究,提出了粗糙形式概念抽取的属性集合幂集方法.其操作要点为:粗糙形式概念的内涵由属性集合幂集方法所求得的子集确定,粗糙形式概念的外延由属性集合幂集所对应对象的上下近似集确定.该方法实现了粗糙形式概念的抽取,...     

一种改进的频繁无规则集集合开采算法

数据挖掘的一个基本任务是在海量数据的数据库中开采频繁项目集。本文提出了一种方法,不用开采频繁项目集全集,而是开采它的一个称为频繁无规则集集合的精简集。我们能用频繁无规则集集合还原出完整的频繁项目集集合和它们的精确支持度而不用读取数据库。可以看到,对频繁无规则集集合的开采是高效的。我们给出了一个算法HOPE-Ⅲ来开采频繁无规则集集合,并将它和算法A-Close进行了比较。实验结果显示,HOPE-Ⅲ在任何情况下都比A-Close的性能更好。     

Design and Implementation of the ROL Deductive Object-Oriented Database System

ROL is a deductive object-oriented database system that has been implemented at the University of Regina. It provides a uniform rule-based declarative language for defining, manipulating and querying databases, which integrates important features of both deductive databases and object-oriented databases. It supports object identity, complex objects, classes, class hierarchies, multiple inheritance with overriding and blocking, and schema definition. It also supports structured values such as functor objects and sets, treating them as first class citizens, and providing powerful mechanisms for representing both partial and complete information about sets. This paper describes its design and implementation. An important novel feature of the implementation is that it combines top-down and bottom-up evaluation strategies and automatically selects a strategy based on the nature of the query and data in the database.     

一个演绎对象数据库SD-DOOD的设计与实现

通过探寻面向对象数据库与知识库技术相结合的途径，研究演绎对象数据库系统实现的关键技术。以基于演绎数据库系统SD-DDBS，设计实现了一个演绎对象数据库系统原型SD-DOOD。系统支持类、类层次、对象、属性、方法、继承和封装等面向对象数据库系统的核心概念，支持演绎对象等演绎数据库的概念，提供了图形用户接口(GUI)，便于用户进行创建、查询等操作。     

DOOL程序语义等价转换为Datalog 程序的转换规则

演绎对象数据库(DOOD)是演绎数据库与面向对象数据库两者优点相结合的产物。笔者设计实现了一个演绎对象数据库系统原型SD-DOOD,它是基于演绎数据库系统SD-DDBS的。然而,它使用的是演绎对象库语言DOOL,而演绎数据库语言是基于Datalog的,因此该文提出了应用一些转换规则来将DOOL程序转换为Datalog,通过规则转换,能求出DOOL程序的最小不动点(即程序值),从而使得系统的查询操作全都由SD-DDBS最终得出结果。文中详细介绍了转换规则的具体内容。     

The Implementation of a Deductive Query Language Over an OODB

The ROCK and ROLL database system cleanly integrates deductive and object-oriented capabilities by defining an imperative programming language, ROCK, and a declarative, deductive language, ROLL, over a common object-oriented (OO) data model. Existing techniques for evaluation and optimization of deductive languages fail to address key requirements imposed by ROLL such as: strict typing; placement of deductive methods (predicates) within classes; encapsulation; overriding and late binding. This paper describes the task of implementing an evaluator and optimizer for ROLL, explaining how existing implementation techniques for deductive languages were adapted to meet these requirements and extended to support novel types of optimization.     

Query language approach based on the deductive object-oriented database paradigm

The integration of data-oriented (structural), behavioral and deductive aspects is necessary in next generation information systems. The deductive object-oriented database paradigm offers a very promising starting point for the implementation of these kinds of information systems. So far in the context of this paradigm a big problem has been the lack of a query language suitable to an ordinary end user. Typically in existing proposals for deductive object-oriented databases the user has to master well both logic-based rule formulation and object-oriented programming. In this paper we introduce a set of high-level querying primitives which increases the degree of declarativeness compared to the deductive object-oriented query languages proposed so far. In terms of these primitives it is possible to offer for end users such application-specific concepts and structures whose interpretation is obvious to users but whose specification is too demanding for them. By combining these primitives in queries the user can integrate data-oriented, behavioral and deductive aspects with each other in a concept-oriented way. Our query language approach is based on the incorporation of deductive aspects to object-orientation. Among others this means that deductive aspects of objects are inherited in the specialization/generalization hierarchy like any other properties of objects.     

Approaches to deductive object-oriented databases

The paper is concerned with the problem of combining deductive and object-oriented features to produce a deductive object-oriented database system which is comparable to those currently available under the relational view of data modelling not only in its functionality but also in the techniques employed in its construction and use. Under this assumption, the kinds of issues that have to be tackled for a similar research strategy to produce comparable results are highlighted. The authors motivate their terms of comparison, characterize three broad approaches to deductive object-oriented databases and introduce the notion of language convergence to help in the characterization of some shortcomings that have been perceived in them. Three proposals that have come to light in the past three years are looked into in some detail, in so far as they exemplify some of the positions in the space of choices defined. The main contribution of the paper is towards a characterization of the language convergence property of deductive database languages which has a key role in addressing critiques of the deductive and object-oriented database research enterprise. A basic familiarity with notions from deductive databases and from object-oriented databases is assumed.     

演绎的面向对象数据库

本文回顾了演绎数据库（ＤｅＤＢ）和面向对象数据库（ＯＯＤＢ）的发展历史，综述了已取得的主要成果，讨论了研究的主要特征、存在的问题以及未来的发展方向。在此基础上，本文着重论述了演绎的面向对象数据库（ＤＯＯＤ）作为集成ＤｅＤＢ和ＯＯＤＢ理论和技术的新领域所涉及到的值得进一步的问题、目前采用的方法和取得的成果。此外，本文还讨论了ＤＯＯＤ系统开发的技术可能性，分析了实现ＤＯＯＤ系统的各种途径的可行性和技术关键。     

集合索引结构及其联接操作

集合类型是面向对象数据库和对象-关系数据库中的一种重要的数据类型.提出了集合类型数据的一种索引结构Set_struc,并提出了基于Set_struc的集合联接算法.Set_struc通过合并集合数据的公共前缀组织数据.这种方法可以减少重复数据和重复模式的存储空间,并通过基于树的联接算法提高集合数据上的联接操作的性能.其性能优于现有的算法,如PSJ(partition based join).     

Overview of emerging database architectures

A database system is a miniworld data repository representing some aspects of the real world. In a database system, information is well organized and has some inherent meaning. In recent years, the emergence of new types of computer applications, such as multimedia and computer-added manufacturing, have resulted in demands to manage complex data types that are beyond the capabilities of existing relational databases. At the same time, new developments in network technologies, artificial intelligence, semantic modeling, and object-oriented programming have inspired research in database topics such as distributed, deductive, object-oriented, active, and deductive and object-oriented databases (DOOD). Essentially, the most promising new database technologies combine the merits of different kinds of database architectures. Starting with the relational database architecture, this paper will review the emerging database technologies, and thereby, provide insight into current and future directions in database technologies.     

A Reasoning Mechanism for DeductiveObject-Oriented Databases

Based on the approach implementing a deductive object-oriented database system through the underlying relational database,this paper presents and object reasoning language O-Datalog,which is the extension of Datalog in form and can deal with object-oriented data.For any O-Datalog program,an dquivalent Datalog program can be built to help evaluate the original program.This paper focuses on the syntax,semantics and evaluation of O-Datalog.