具有多时间粒度的时态数据库初等关键字、简单范式分解问题研究

一个好的数据库逻辑设计目标是消除数据冗余以及插入、删除和更新异常．对于时态数据库也是如此．提出了时态初等函数依赖、时态初等关键字、时态简单关键字等概念,在此基础上利用具有多时间粒度的时态函数依赖（TFD）约束对时态数据库进行了规范化研究,提出了规范程度高于时态三范式低于时态Boyce—Code范式的时态初等关键字范式（TEKNF）及时态简单范式（TSNF）,并研究了时态初等关键字范式和时态简单范式的分解问题,给出了相关分解算法,并对算法的可终止性、正确性进行了证明,对时间复杂度进行了分析．     

偏序环境下时态数据库中的TBCNF分解问题研究*

针对偏序时态数据库进行研究,提出了非严格偏序时态类型集、偏序时态模块模式、偏序TFD集的模式投影、偏序时态模块投影和偏序时态BC范式等概念,并给出了避免时态类型间复杂操作的偏序时态BC范式的分解算法,对其正确性、可终止性进行了证明,并对算法的时间复杂度进行了分析。为偏序时态数据库的规范化设计奠定了基础。     

全序时态模块模式的TO_TSNF分解问题研究

在许多时态数据库应用中，都存在着涉及多时间粒度的约束。但是，具有多时问粒度的时态数据库的设计相当复杂，甚至难以实现，而现实世界中的许多应用所涉及到的时态类型集都能满足全序关系。同时，具有全序时态类型集的全序时态模块模式有着良好的特性，因此本文提出了全序时态模块模式、时刻关系模式、全序时态模块投影、全序时态简单候选关键字、全序时态三范式（TO_T3NF）和全序时态简单范式（TO_TSNF）等概念，并给出了全序时态简单范式的分解算法，对其正确性进行了证明，并对时间复杂度进行了分析。     

偏序时态模式下规范覆盖问题*

目前有效的多时间粒度时态数据库设计方法多针对全序时态模式,当时态模式的时态类型集为偏序集时,由于涉及时态类型间的最大下界等操作而使其难以实现。针对偏序时态模式的规范覆盖问题进行研究,提出了偏序TFD（时态函数依赖）集有限闭包、偏序模式属性集有限闭包、偏序无冗余覆盖和偏序规范TFD集等概念,解决了偏序TFD成员籍问题;并给出了偏序TFD集的规范覆盖算法,对其正确性进行了证明,对算法的时间复杂度进行了分析。为偏序时态模式的综合范式分解问题研究奠定基础。     

一个多时间粒度下时态模式的T3NF分解算法

对于时态数据库，时间维的引入使得如何有效地进行数据库设计以消除数据冗余和插入、删除异常显得尤为重要．可以通过支持多时间粒度的时态函数依赖（TFDs）约束对时态数模式进行规范化．但是多时间粒度的使用给数据库设计带来巨大的复杂性．一般来说，系统所能处理的和相当多的应用所涉及到的时态类型集满足全序关系．对于这种具有全序时态类型集的时态模式，通过分析TFD臬所具有的良好特性，给出了一个得到满足时态第三范式（T3NF）的无损分解的多项式时间的算法．     

模糊时态数据库设计中模糊/时态向量空间特性研究

数据库设计的目标是生成一组模式,使数据存储既减少冗余,又可方便地获取信息。这是通过设计满足适当范式的模式来实现的。函数依赖FD是有效的工具。对于多粒度模糊时态数据库设计来说,模糊值和多粒度模糊时态序列的映射关系是将传统FD扩展到模糊时态函数依赖FTFD的关健,通过分析属性集的有限闭包、时态类型集的封闭集、属性集在给定时态上的依赖等概念,得到模糊/时态向量的特征描述,并对此方法的正确性进行了论证。此方法能方便地在计算机上表达模糊属性值和模糊时态序列的映射关系,为模糊时态数据库范式的判定和分解算法提供有效的手段。     

具有多时间粒度的时态多值依赖及时态模式分解方法研究

一个好的数据库逻辑设计目标是消除数据冗余以及插入、删除和更新异常.对于时态数据库,通过具有多时间粒度的时态函数依赖约束对时态数据库进行规范化已有大量研究.基于时态函数依赖和多值依赖理论提出了多时间粒度约束的时态多值依赖(TMVD)等概念,并给出了时态多值依赖的推理规则,对其有效性、完备性进行了证明.由于包含有限个TMVD的TMVD集通常蕴含着无限个TMVD,给出了TMVD的有限推理规则,对其有效性、完备性进行了证明.最后,基于时态多值依赖集提出了时态第四范式,并给出了时态模式的T4NF的无损分解算法,对算法的可终止性、正确性进行了证明,并对时间复杂度进行了分析.     

全序时态模块模式的TO_TBCNF分解问题研究

时间粒度是所有时态数据所拥有的共同特点。在许多时态数据库应用中,都涉及多时间粒度约束,但是,具有多时间粒度的时态数据库的设计相当复杂,难以实现。而现实世界中的许多应用涉及到的时态类型集都能满足全序关系,由于具有全序时态类型集的全序时态模块模式有着良好的特性,文章提出了全序时态模块模式、时刻关系模式、全序时态模块投影和全序时态BC范式（TO_TBCNF）等概念,并给出了全序时态BC范式的分解算法,对其正确性、可终止性进行了证明,并对时间复杂度进行了分析。     

具有多时间粒度的强全序时态模式中多值依赖问题研究

在时态数据库中存在着与时态多值依赖相关的存储冗余、更新异常等问题.但由于时态多值依赖的复杂性,使得根据时态多值依赖所进行的范式分解并不能总保持无损联接,为此对强全序时态模式中时态多值依赖与无损分解的相关性进行了深入研究,给出了规则的时态多值依赖(RTMVD)和属性集的时间粒度等概念,并给出了RTMVD的一套有效的推理规则,针对强全序时态模式中时态多值依赖与无损分解的相关性给出了相关定理,解决了规则的时态多值依赖环境下时态模式在多粒度上的无损分解问题,为规则时态多值依赖环境下时态模式的进一步规范化奠定了基础.     

基于约束的XML文档规范化算法

XML模式设计是XML数据库设计的关键．基于XML文档的基本概念给出了XML部分函数依赖、传递函数依赖、XML范式、XML第1到第3范式以及DTD无损联接分解的相关定义,提出XML模式规范化转换规则,给出无损联接分解的两种规范化算法,对算法的正确性、可终止性和时间复杂性进行了证明分析,并实验证明了规范化后的文档查询和存储效率有明显的提高．这将对未来的XML函数依赖保持、XML多值依赖以及XML模式设计的进一步规范化研究奠定理论基础．     

XML函数依赖研究综述

函数依赖作为数据库规范化的基础在关系理论中起着重要的作用。近年来，XML得到广泛应用并已成为互联网上数据传输和交换的标准。由于XML半结构化的特性，使得如何定义XML函数依赖使其具有更强的描述能力，以及如何解决相应的逻辑蕴涵问题成为当今学术界所面临的挑战。针对这些问题，系统地描述了目前关于XML函数依赖的研究现状，特别是把分析的重点放在如何定义函数依赖、判断其蕴涵关系以及从XML文档中发现函数依赖等问题上。最后讨论了诸如类型化函数依赖关系等一些相关的研究方向。     

Extending existing dependency theory to temporal databases

Normal forms play a central role in the design of relational databases. Several normal forms for temporal relational databases have been proposed. These definitions are particular to specific temporal data models, which are numerous and incompatible. The paper attempts to rectify this situation. We define a consistent framework of temporal equivalents of the important conventional database design concepts: functional dependencies, primary keys, and third and Boyce-Codd normal forms. This framework is enabled by making a clear distinction between the logical concept of a temporal relation and its physical representation. As a result, the role played by temporal normal forms during temporal database design closely parallels that of normal forms during conventional database design. These new normal forms apply equally well to all temporal data models that have timeslice operators, including those employing tuple timestamping, backlogs, and attribute value timestamping. As a basis for our research, we conduct a thorough examination of existing proposals for temporal dependencies, keys, and normal forms. To demonstrate the generality of our approach, we outline how normal forms and dependency theory can also be applied to spatial and spatiotemporal databases     

Adding inclusion dependencies to an object-oriented data model with uniqueness constraints

We study an object-oriented data model that allows to express both uniqueness constraints and inclusion dependencies as semantic constraints. The data model is based on a subset of F-logic. Uniqueness constraints comprise path functional dependencies which generalise functional dependencies and reflect the navigational power of object-oriented query languages. As inclusion dependencies, we consider explicit class inclusion constraints, besides inclusions required by class hierarchies, and onto constraints that enforce reachability of objects. For these classes of semantic constraints we present an axiomatisation and prove its inference rules to be correct and complete with respect to general logical implication, leaving the decision problem open. The completeness proof combines the known construction for path functional dependencies alone with a possibly infinite model generation process to enforce onto constraints. The results prepare the grounds for normal forms in object-oriented data models and subsequently for computer aided object-oriented database design, following the decomposition approach for the relational data model. Beyond the application for schema design, the achievements could also be exploited for related tasks like semantic query optimisation and mediated data integration within a variety of graph based data models. Received: 11 October 2000 / 27 January 2003     

Normalization and lossless join decomposition of similarity‐based fuzzy relational databases

Fuzzy relational database models generalize the classical relational database model by allowing uncertain and imprecise information to be represented and manipulated. In this article, we introduce fuzzy extensions of the normal forms for the similarity‐based fuzzy relational database model. Within this framework of fuzzy data representation, similarity, conformance of tuples, the concept of fuzzy functional dependencies, and partial fuzzy functional dependencies are utilized to define the fuzzy key notion, transitive closures, and the fuzzy normal forms. Algorithms for dependency preserving and lossless join decompositions of fuzzy relations are also given. We include examples to show how normalization, dependency preserving, and lossless join decomposition based on the fuzzy functional dependencies of fuzzy relation are done and applied to some real‐life applications. © 2004 Wiley Periodicals, Inc. Int J Int Syst 19: 885–917, 2004.     

具有全序时态类型集时态函数依赖集的研究

好的数据库逻辑设计目标是消除数据冗余以及插入、删除和更新异常.对于时态数据库,可以通过具有多时间粒度的时态函数依赖(TFDs)约束对时态数模式进行规范化.但是由于时间维的引入和多时间粒度的使用而给数据库设计带来巨大的复杂性.一般来说,系统所能处理的和相当多的应用所涉及到的时态类型集满足全序关系,并且具有全序时态类型集的TFD集的推导规则与传统函数依赖(FDs)的Armstrong公理有着紧密的联系.通过分析TFDs与FDs之间存在的联系,利用传统FD集的相应算法,提出了成员籍、有限属性闭包等TFD集的一些重要算法.这些算法是时态数据库进一步规范化的基础.     

时态类型集的封闭集

好的数据库逻辑设计目标是消除数据冗余以及插入和删除异常。对于时态数据库，可以利用具有多时间粒度的时态函数依赖（TFDs）约束对时态数据库进行规范化。要进行有效的数据库设计，需要解决有限属性闭包和成员籍等一些有关TFD的问题。为了方便计算机对时态类型的处理和找到有效的解决TFD的相关问题的算法，该文提出了封闭时态类型集的概念，并且给出了一个求给定TFD集的封闭集的算法。     

时态函数依赖多值依赖混合集的成员籍问题研究

对于TFD和TMVD混合集约束的时态模式来说，由于多时间粒度的使用使成员籍问题的解决变得更加复杂．由于成员籍问题的解决对设计有效的模式分解算法必不可少，由此定义了时态类型集的强封闭集、属性集的有限闭包、属性集在给定时态类型上的有限依赖基、属性集的有限依赖基及特殊有限依赖基等概念，给出了求属性集的有限闭包、有限依赖基和特殊有限依赖基、时态混合集成员籍问题的算法，并对算法的可终止性、正确性进行了证明，对时间复杂性进行了分析，     

A general treatment of dynamic integrity constraints

This paper introduces a general, set-theoretic model for expressing dynamic integrity constraints, i.e., integrity constraints on the state changes that are allowed in a given state space. In a managerial context, such dynamic integrity constraints can be seen as representations of “real world” constraints and business rules. This topic has important practical applications in many business areas. The notions of (direct) transition, reversible and irreversible transition, transition relation, and consistency of a transition relation will be introduced. The expected link with Kripke models (for modal and temporal logics) is also made explicit. Several practical examples of dynamic integrity constraints will illustrate the applicability of the theory. Some important subclasses of dynamic integrity constraints in a database context will be identified, e.g., various forms of cumulativity (which can be regarded as “transitional” inclusion dependencies concerning two different “points in time”), non-decreasing values, integrity constraints on initial and final values, life cycles, changing life cycles, and transition and constant dependencies. Several formal properties of these dependencies will be derived. For instance, it turns out that functional dependencies can be considered as “degenerated” transition dependencies. Also, the distinction between primary keys and alternate keys is reexamined, from a dynamic point of view.     

The theory of functional and template dependencies

Template dependencies were introduced by Sadri and Ullman [17] to generalize existing forms of data dependencies. It was hoped that by studying a large and natural class of dependencies, we could solve the inference problem for these dependencies, while that problem was elusive for restricted subsets of the template dependencies, such as embedded multivalued dependencies. At about the same time, other generalizations of known dependency forms were developed, such as the implicational dependencies of Fagin [11] and the algebraic dependencies of Yannakakis and Papadimitriou [20]. Unlike the template dependencies, the latter forms include the functional dependencies as special cases. In this paper we show that no nontrivial functional dependency follows from template dependencies, and we characterize those template dependencies that follow from functional dependencies. We then give a complete set of axioms for reasoning about combinations of functional and template dependencies. As a result, template dependencies augmented by functional dependencies can serve as a substitute for the more general implicational or algebraic dependencies, providing the same ability to represent those dependencies that appear ‘in nature’, while providing a somewhat simpler notation and set of axioms than the more general classes.     

Learning Sets of Antecedent-restricted Functional and Multivalued Dependencies with Queries

Identifying dependencies that hold in relational databases is essential to produce good databases designs. In particular, functional and multivalued dependencies are used to obtain relation schemes that satisfy the 4th normal form, a property that is considered satisfactory for most applications. It is known that the class of sets of functional dependencies is learnable in the exact model of learning with queries. Also a subclass of multivalued dependencies, the class of consequent-restricted multivalued dependencies, has been shown to be learnable in this model. In this paper, we present an algorithm that learns a class that contains sets of both functional and multivalued dependencies under some restrictions imposed on the antecedents of dependencies. We also show, as a by-product, an algorithm that learns a non-trivial subclass of 2-quasi Horn formulas, closely related to the class just mentioned.