A structure-based model of semantic integrity constraints for relational data bases

Data base management systems (DBMSs) are in widespread use because of the ease and flexibility with which users access large volumes of data. Ensuring data accuracy through integrity constraints is a central aspect of DBMS use. However, many DBMSs still lack adequate integrity support. In addition, a comprehensive theoretical basis for such support—the role of a constraint classification system—has yet to be developed. This paper presents a formalism that classifies semantic integrity constraints based on the structure of the relational model. Integrity constraints are characterized by the portion of the data base structure they access, whether one or more relations, attributes, or tuples. Thus, the model is completely general, allowing the arbitrary specification of any constraint. Examples of each type of constraint are illustrated using a small engineering data base, and various implemention issues are discussed.     

Structure of closures in relational schemas with join and functional dependencies

Translations of relational schemas are extended to the set of functional and join dependencies. A basic theorem on the representation of the closure of an attribute subset is proved.Translated from Kibernetika, No. 5, pp. 18–26, September–October, 1990.     

从关系数据库构建语义丰富本体的方法

网络中大量数据存储在关系数据库中,利用这些数据资源构建领域本体是实现语义Web的任务之一。制定了一组优化的通用转换规则(特别注重对元组信息的语义分析与挖掘),结合领域专家的选择判断,在尽量保留和挖掘关系数据库语义信息的基础上,给出了一个从关系数据库半自动构建OWL本体的方法,同时利用WordNet对本体进行语义丰富,并最终通过系统实现转换过程。     

A full-screen facility for defining relational andentity-relationship database schemas

An easy-to-use, interactive facility for defining schemas for a mainframe database system has been developed that is more convenient than a linear language. The facility called Dbdefs, has several features that make it easy to use. It provides similar interfaces for defining schemas for two data models, relational and entity-relationship. An overview of Dbdefs is followed by discussion of the relational and entity-relationship interfaces     

A case study in mapping conceptual designs to object‐relational schemas

The recent emergence of object‐relational technology into the commercial database market has caused new challenges for the implementation of conceptual database designs. This paper presents our experience with using the Oracle 8 object‐relational data model in the implementation of an engineering application described using the EXPRESS conceptual modeling language. EXPRESS is part of the engineering community's Standard for the Exchange of Product Data and can be characterized as a structurally object‐oriented modeling language, supporting the notion of entities, entity hierarchies, complex constraints on entity hierarchies, relationships and inverse relationships between entities, and user‐defined types. As a result, EXPRESS provides an excellent framework for studying the mapping of conceptual modeling concepts into an object‐relational model. In this paper, we describe the way in which the features of EXPRESS can be mapped into object‐relational features such as object tables, object references, and nested tables. We also describe the manner in which features such as member functions on object types, triggers, and stored procedures can be used to support the implementation of constraints associated with a conceptual schema. Although the mappings presented are specific to EXPRESS and Oracle 8, the mappings are generalizable to conceptual modeling languages and object‐relational models with similar features. Our work defines how traditional mapping concepts must be revised in order to make adequate use of the features now found in object‐relational models. As part of this paper, we also compare our mapping approach using Oracle 8 to mapping issues for the PostgreSQL object‐relational model and the Objectivity/DB object‐oriented data model. Copyright © 2000 John Wiley & Sons, Ltd.     

Finite satisfiability of integrity constraints in object-orienteddatabase schemas

Checking satisfiability of database constraints is a fundamental problem in database design. In addition, database constraints have to be not only satisfiable but also finitely satisfiable. This problem is generally addressed by using theorem provers that, being developed for first order logic formulas, are based on semidecidable procedures. Furthermore, even in simple cases, theorem provers are quite inefficient in dealing with comparison operators such as, for instance, the equality. In this paper, a decidable, sound, and complete method for checking finite satisfiability of a specific class of integrity constraints for object-oriented databases, including the equality constraints, is presented. The method, that is based on a graph-theoretic approach, has exponential complexity in the worst case, rarely occurring in practice     

On the equivalence of data base schemas—a semantic approach to data translation

A notion of the equivalence of data is the basis for deriving a correct translation of data bases. The equivalence of data base states and data base schemas is defined. Since this definition can only be given with respect to the semantics of data, a short discussion of data base semantics is given. It is shown, how a semantic data model and data definition language (LDDL) can be used to construct a correct specification of a translation function. Finally, an example of the translation of a CODASYL data base schema to a relational data base schema is given.     

基于本体的关系数据库语义检索

以经济学领域本体为例,首先研究SemSORD基本原理和方法,然后提出基于关系数据库关键词检索(Keyword Search over Relational Databases,KSORD)技术实现的关系数据库语义检索模型,并实现相应的原型系统Si-SEEKER,最后提出该领域的研究挑战和技术发展趋势.     

XML文档DTD到关系模式的转换

随着XML技术的不断发展和成熟,如何有效的利用关系数据库技术存储和查询XML文档显得非常重要。提出了一种XML文档DTD到关系表格的两阶段转换法,先将DTD文件映射为XSchema模式,通过对XSchema模式的约束简化、内联、添加键约束、数据类型和属性转换得到能够在RDBMS中存储的关系模型,映射后XML文档信息不会发生丢失且能保持键约束。实例的成功转换表明了该方法的可行性。     

From keywords to relational database content: A semantic mapping method

Keyword-based query specification to extract data from structured databases has attracted considerable attention from various researchers, and many interesting proposals may be found in the scientific literature. However, many of these studies focus on finding a set of interconnected tuples containing all or some of the query keywords. The architecture introduced by this paper covers from the selection of databases on the Web to ranked relevant results. The approach also includes important aspects such as the proximity between keywords, query segmentation, and the use of aggregate functions, among others. The empirical evaluation analyzes the relevance of results and proves competitive as regards related studies.     

Constructing the Bayesian network structure from dependencies implied in multiple relational schemas

Relational models are the most common representation of structured data, and acyclic database theory is important in relational databases. In this paper, we propose the method for constructing the Bayesian network structure from dependencies implied in multiple relational schemas. Based on the acyclic database theory and its relationships with probabilistic networks, we are to construct the Bayesian network structure starting from implied independence information instead of mining database instances. We first give the method to find the maximum harmoniousness subset for the multi-valued dependencies on an acyclic schema, and thus the most information of conditional independencies can be retained. Further, aiming at multi-relational environments, we discuss the properties of join graphs of multiple 3NF database schemas, and thus the dependencies between separate relational schemas can be obtained. In addition, on the given cyclic join dependency, the transformation from cyclic to acyclic database schemas is proposed by virtue of finding a minimal acyclic augmentation. An applied example shows that our proposed methods are feasible.     

CEVCLUS: evidential clustering with instance-level constraints for relational data

Recent advances in clustering consider incorporating background knowledge in the partitioning algorithm, using, e.g., pairwise constraints between objects. As a matter of fact, prior information, when available, often makes it possible to better retrieve meaningful clusters in data. Here, this approach is investigated in the framework of belief functions, which allows us to handle the imprecision and the uncertainty of the clustering process. In this context, the EVCLUS algorithm was proposed for partitioning objects described by a dissimilarity matrix. It is extended here so as to take pairwise constraints into account, by adding a term to its objective function. This term corresponds to a penalty term that expresses pairwise constraints in the belief function framework. Various synthetic and real datasets are considered to demonstrate the interest of the proposed method, called CEVCLUS, and two applications are presented. The performances of CEVCLUS are also compared to those of other constrained clustering algorithms.     

基于本体的关系数据库语义检索

以经济学领域本体为例,首先研究SemSORD基本原理和方法,然后提出基于关系数据库关键词检索(Keyword Search over Relational Databases,KSORD)技术实现的关系数据库语义检索模型,并实现相应的原型系统Si-SEEKER,最后提出该领域的研究挑战和技术发展趋势。     

Composing semantic Web services under constraints

Web service composition is an inevitable aspect of Web services technology, which solves complex problems by combining available basic services and ordering them to best suit the problem requirements. Automatic composition gives us flexibility of selecting best candidate services at composition time satisfying QoS requirements; this would require the user to define constraints for selecting and composing candidate Web services. In this work, a Web service composition approach is presented in which a rich set of constraints can be defined on the composite service. The output of the framework is the schedule of Web service composition in which how and when services are executed is defined. The basic properties of the proposed approach is converting Web service composition problem into a constraint satisfaction problem in order to find the best solution that meets all criteria defined by user and providing semantic compatibility and composability during composition.     

类——关系数据库之间的映射

面向对象的开发方法是目前软件开发的主要方法，它以类作为软件分析，设计和实现的基本单元，而关系数据库则是许多人都青睐的持久信息存储方法，所以类－－关系数据库之间的映射是开发者必须关注的一件大事，文章扼要地介绍了类－－关系数据库之间的映射原则。     

Cardinality constraints in semantic data models

Constraints are central to the notion of a semantic data model. How well a model captures constraints affects its power and viability as a semantic data model. Cardinality constraints are an important subclass of general constraints. In this paper we provide formal definitions for cardinality constraints of several semantic models, as described in the literature. We construct a partial ordering of these constraints that shows the relative power expressed by each cardinality constraints. We discuss our results and offer possible extensions to contemporary cardinality constraint definitions. Our contributions include a collection and formal definition of existing cardinality constraints, a partial ordering of this set, and recommendations for cardinality constraint mechanisms in semantic data models.     

基于C_Schema的XML模式到关系模式的映射

为解决复杂XML文档中的递归元素、多命名空间信息、重复结构、面向未来可扩展元素和属性等关系模式的映射,针对P_Schema和B_Schema在XML模式到关系模式映射中的不足,提出了一种基于C_Schema的XML模式到关系模式的映射方法。C_Schema对P_Schema和B_Schema进行了继承和扩展,将上述复杂信息提取出来生成新类型,并在其相应的父元素中保留对新类型的引用。C_Schema与XML Schema模式是一种等价关系,根据一定的映射规则,将C_Schema直接映射为关系模式,实现将XML文档在数据库中的存储。依据该模式可实现各种基于模式的复杂XML文档到关系数据库的存储与还原,可广泛应用于各种基于XML的行业标准中。     

一种DTD一致性的判定方法

DTD作为一种XML文档结构的模式语言得到了广泛的使用,它描述了相似的XML文档的结构。DTD的一致性是指对于一个给定的DTD,判断是否存在至少有一个XML文档满足DTD。在引入DTD一致性的形式化定义的基础上,分析了引起DTD不一致性的各种因素,提出了DTD一致性的判定方法。     

带约束本体语义扩展的信息过滤算法

提出一种基于本体的信息过滤方法。该方法通过本体实现形式化语义描述,并对原始输入条件进行带约束规则的本体语义扩展。进而为了实现语义匹配,给出了信息向量语义描述及权重计算方法。最终,实现基于语义相似度计算的信息过滤。实验证明,该方法是有效的。