数据修复与一致性查询处理研究

在数据库以及集成系统中通常存在违背数据约束的不一致查询问题。修复是解决该问题的主要手段之一,但目前还缺乏基于修复、约束与查询的统一模型研究。提出了基于删除元组修复、满足多种类型约束的一致性查询算法;阐明了具有简洁特性的约束定义与查询语句结构;构建了新的查询与修复系统模型,将关系实例集、非空的约束集、查询定义、修复方法等统一到模型中,以产生满足一致性约束要求的查询结果。所研究的方法、语言以及模型通用性强、适用面广,不局限于特定质量问题的修复与查询。     

Methodology and intermediate layer for the automatic creation of ontology instances stored in relational databases

In this paper, we introduce our solution for mapping local ontologies to relational and object‐oriented representations. This solution is part of the GeoNis framework for the interoperability of geo‐information systems applications in a local community environment. The GeoNis framework is based on a hybrid ontology approach for data integration. Therefore, a very important subject in our research on semantic data integration is the creation of mapping between a spatial information source and its local ontology. We developed the OWL2RDB mapping language to create an intermediate layer between a relational database and the OWL ontology. This intermediate layer contains rules (expressed in the OWL2RDB language) for mapping between the structural elements of a relational database and the concepts of OWL ontologies. We also present a system that uses the OWL2RDB intermediate layer to create classes that can handle ontology instances stored in relational databases. We have developed a prototype for a tool that uses this proposed approach for the automatic generation of translator/wrapper components in the GeoNis interoperability environment. Copyright © 2012 John Wiley & Sons, Ltd.     

基于语义近似逼近技术的多代理协作

本体在多代理系统中起着重要的作用，它提供和定义了一个共享的语义词汇库。然而，在现实的多代理通讯的过程中，两个代理共享完全相同的语义词汇库是几乎不可能的。因为信息不完整以及本体的异构等特性，一个代理只能部分理解另外一个代理所拥有的本体内容，这使得代理间的通讯非常困难。本文就是探索利用近似逼近技术实现基于部分共享分布式本体的多代理通讯，从而实现多代理之间的协作查询。我们使用基于OWLweb本体语言的描述逻辑来描述分布式本体的近似查询技术。最终我们也开发了基于语义近似逼近方法的一个多代理协调查询系统。     

基于本体的关系数据集成的查询处理

为实现异构关系数据库的语义集成,针对传统集成技术存在的问题,在对语义网等相关技术进行分析的基础上,研究基于本体的关系数据集成系统中的查询处理问题,提出了一种基于本体的关系数据库集成框架。设计了基于本体的关系数据的描述方法,使用本体作为集成的全局模式来描述关系模式的语义。设计了查询重写算法,该算法可以将基于全局模式的SPARQL查询重写为针对具体关系数据库的查询,从而实现对异构关系数据库的集成。实验表明,该算法具有良好的可扩展性。     

一种面向领域的虚拟视图语义集成方法*

针对油井工程领域异构数据源,提出了一种基于语义的虚拟视图集成方法。通过本体抽取和本体合并分别构造数据源局部本体和全局本体实现基于语义的数据访问视图,并利用全局本体、局部本体和数据源模式之间的映射关系,将基于语义的查询转换为底层数据源的访问请求,提供统一、透明的数据访问视图,以避免数据加载和更新等问题。通过油井决策支持数据集成平台,该方法取得了很好的应用效果。     

Logic-based query optimization for object databases

We present a technique for transferring query optimization techniques, developed for relational databases, into object databases. We demonstrate this technique for ODMG database schemas defined in ODL and object queries expressed in OQL. The object schema is represented using a logical representation (Datalog). Semantic knowledge about the object data model, e.g., class hierarchy information, relationship between objects, etc., as well as semantic knowledge about a particular schema and application domain are expressed as integrity constraints. An OQL object query is represented as a logic query and query optimization is performed in the Datalog representation. We obtain equivalent (optimized) logic queries, and subsequently obtain equivalent (optimized) OQL queries for each equivalent logic query. We present one optimization technique for semantic query optimization (SQO) based on the residue technique of U. Charavarthy et al. (1990; 1986; 1988). We show that our technique generalizes previous research on SQO for object databases. We handle a large class of OQL queries, including queries with constructors and methods. We demonstrate how SQO can be used to eliminate queries which contain contradictions and simplify queries, e.g., by eliminating joins, or by reducing the access scope for evaluating a query to some specific subclass(es). We also demonstrate how the definition of a method or integrity constraints describing the method, can be used in optimizing a query with a method     

OWL本体到关系数据库模式的映射

通过对现有本体存储模式的分析,以及对OWl本体和关系数据库模式之间的概念对应关系的分析,定义了从OWL本体到关系数据库模式的转换规则,给出了OWL本体存储模式的设计原则,并基于该原则提出了一种新的本体存储模式.针对本体描述语言OWL的构词特点,该模式提出将本体中的语义信息存放在不同的表中,以达到方便理解、结构稳定和提高效率的目的,适应于多数中小型本体的存储.     

A Data Model for Data Integration

Data integration systems provide a uniform query interface (UQI) to multiple, autonomous data sources [Alon Y. Halevy. Answering queries using views: A survey. The VLDB Journal, 10(4):270–294, 2001]. This paper presents the universal data model (UDM) that captures the semantically salient aspects of relational, entity-relationship, and XML data models. As a consequence, UDM — including its accompanying query language — provides a simple and elegant UQI for integrating data represented in some of the most widely adopted data models.     

A Methodology to Create Legal Ontologies in a Logic Programming Based Web Information Retrieval System

Web legal information retrieval systems need the capability to reason with the knowledge modeled by legal ontologies. Using this knowledge it is possible to represent and to make inferences about the semantic content of legal documents. In this paper a methodology for applying NLP techniques to automatically create a legal ontology is proposed. The ontology is defined in the OWL semantic web language and it is used in a logic programming framework, EVOLP+ISCO, to allow users to query the semantic content of the documents. ISCO allows an easy and efficient integration of declarative, object-oriented and constraint-based programming techniques with the capability to create connections with external databases. EVOLP is a dynamic logic programming framework allowing the definition of rules for actions and events. An application of the proposed methodology to the legal web information retrieval system of the Portuguese Attorney General’s Office is described.     

db4OWL: An Alternative Approach to Organizing and Storing Semantic Data

The complex structure of semantic data still poses a challenge in storing, querying, and organizing Web information. Although researchers have proposed various semantic database system approaches over the years, it seems that most systems have tried to provide industrial-strength scalability too soon. Consequently, most semantic databases still rely on the relational model of storing data and still use SQL-like query languages for data retrieval. The db4OWL semantic database prototype addresses many of the shortcomings of current systems and features native OWL-querying as well as the ability to store and query multiple ontologies concurrently.     

关系数据库模式和本体间映射的研究综述

关系数据库模式和本体问映射是语义网研究中的一个重要问题.首先,给出关系数据库模式和本体间映射的形式化定义,并从建模思想和应用场景两个方面分析问题的难点.根据3个不同角度,即模型转换的途径、映射策略的适用范围以及映射结果的表达形式,调研当前存在的多种解决途径.在此基础上,进一步介绍并比较6个具有代表性的关系数据库模式和本体间映射的工具.最后,讨论存在的挑战,并指出未来可能的研究方向.     

Virtual database technology: transforming the Internet into adatabase

Much of the world's data lies outside relational databases-scattered across Web sites, file systems, nonrelational databases, and legacy applications. These data sources differ in the way they organize data, in the vocabulary they use, and in their data-access or query mechanisms. These differences make it difficult to combine data from multiple sources. Virtual database (VDB) technology makes external data sources act as an extension of an enterprise's relational database system. Using VDB technology, applications can make powerful queries of data scattered over a variety of sources. The VDB gathers, structures, and integrates the data from these sources, and gives the application programmer the appearance of a single, unified RDBMS     

一种基于Ontology的数据集成系统

针对异构数据源中实现基于语义的数据集成的需求，采用分层思想，在用户层与实际数据层之间增加一个中间层来屏蔽底层数据的异构，用本体作为公共语义描述工具，建立本体到各数据源的映射规则，设计实现了将基于本体的全局查询转化为基于各数据源的局部查询系统，解决了数据源之间的语义异构问题，其中用OWL表示本体和映射，并研究了系统中的关键技术。     

An interface between object-oriented databases and relational databases

Currently relational databases are widely used, while object-oriented databases are emerging as a new generation of database technology. This paper presents a methodology to provide effective sharing of information in object-oriented databases and relational databases. The object-oriented data model is selected as a common data model to build an integrated view of the diverse databases. An object-oriented query language is used as a standard query language. A method is developed to transform a relational data definition to an equivalent object-oriented data definition and to integrate local data definitions. Two distributed query processing methods are derived. One is for general queries and the other for a special class of restricted queries. Using the methods developed, it is possible to access distributed object-oriented databases and relational databases such that the locations and the structural differences of the databases are transparent to users.     

一种支持异构数据库集成的定义说明语言

提出了一种数据集成中间件Mediator定义说明语言，该语言通过提供了一套抽象的语言成分组件，能支持从一个高度抽象的层次来表达复杂数据集成语义，有效解决异构数据源集成时面临的结构/语义异构冲突，并自动生成数据集成中间件Mediator。介绍数据集成定义说明语言（DISL）主要语言成分组件的语法/语义、构造生成Mediator的方法以及应用体系结构，并讨论DISL-Mediator的内部体系结构和它的静态/动态特性.