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。     

基于语义的信息集成系统研究

语义网技术的发展为传统的信息集成领域带来了新的契机,构建基于语义的信息集成系统对于知识的表示、信息的组织与检索等有着重要的意义.通过对领域本体的构建方法和对基于本体的数据集成方法的分析,提出一种基于语义的信息集成模型,改进了传统的基于视图的查询响应方法,在传统的数据库层上构建了RDF/OWL视图,实现了关系模式向本体模式的转换,将SPAROL向SQL转化的查询处理运用于查询重写中.从技术与应用的角度论证了系统的可行性.     

结构工程语义网格本体模型框架的设计与实现

针对结构工程领域中信息集成与共享时碰到的语义冲突问题,基于网格计算和语义Web的相关技术规范,设计和实现结构工程语义网格体系结构.并在此基础上,着重分析在构建结构工程语义网格语义层的过程中,在实例集成、模式集成、概念集成和查询应用几个阶段的语义冲突问题,设计与初步实现语义层本体模型框架.     

基于领域本体和关系模型的XML语义集成方法研究

由于缺乏足够的语义信息,不同模式的XML数据之间很难进行互操作。针对油气井工程中的XML数据集成需求,借助领域全局本体,提出一种模式无关的XML语义集成方法。该方法首先在XML Path路径与领域本体之间进行语义映射,屏蔽其模式差异;然后,按照模型映射方法将XML存储为关系数据;最后通过查询重写将SPARQL转换为SQL语句,实现语义查询。该方法对XML模式进行语义标注,利用关系数据库存储与查询XML数据,能有效处理领域XML数据的语义集成。     

基于Ontology映射的异构信息源查询处理

企业中存在大量语义异构数据源，语义异构阻碍了数据源的查询处理。该文针对这个问题，提出了基于Ontology的语义集成方法，给出了语义异构信息源的查询处理。通过实例验证了方法的可行性。某航空研究所应用表明：该方法可以有效地处理企业中存在的异构数据源查询问题。     

基于XML的异构数据集成系统的查询处理

讨论了基于XML的Web异构数据源集成系统中的查询处理,并提出了针对全局视图的语义缓存的实现方法,包括查询与缓存入口的匹配算法,网络环境下缓存建立和淘汰算法;最后描述了Gav模式集成方式下的查询分解和优化方法。     

基于本体的XML语义集成研究

针对具有相同语义的XML数据经常具有不同表达形式的问题，采用了基于本体的语义集成方法来集成异构XML数据源，即通过一系列映射规则将XPath的局部路径与本体关联起来，将用户的RDQL查询重写为基于XML的XQuery查询，从而达到语义集成的效果。本方法的意义在于用户可以通过本体查询异构的XML数据源。     

应用本体解决面向语义的信息集成中的查询处理

面向语义的信息集成中基于Web的查询处理应用本体来解决在多个领域中检索数据可能产生的语义层的异构,对于在统一的用户界面下提交的查询请求,根据语义,从Web上搜索相关领域的信息,最终将结果显示在用户界面上.该过程是通过查询分解、子查询转换、分发子查询和子查询结果收集及语义转换来完成的.同时,考虑到基于Web的信息查询一般要涉及多个分布的数据源,查询的响应时间要依赖于网络的传输速度,一般来讲比较长,还借鉴了缓存系统的思想,在查询处理架构中引入了缓存数据库,有选择地存放最常用的查询信息,以提高整个查询的速度.     

异构专利数据源集成系统中查询的研究

为了有效地对异构专利数据源进行统一的查询,提出一个基于本体的异构专利数据源集成系统.该系统引入本体解决数据源集成中存在的语义异构,通过全局数据模式为用户提供统一的查询接口,将用户针对全局数据模式的查询重写为针对各个局部数据源的子查询.使用该系统,用户可以从异构的专利源中得到正确的查询结果.     

基于本体的Deep Web查询接口集成

Deep Web中的海量信息只能通过查询接口访问获得,为了能够同时访问同一领域多个Web数据库,需要对多个Web数据库的查询接口进行集成.因此,引入本体技术,提出基于本体的Deep Web查询接口集成方法.Deep Web查询接口集成主要完成两个方面的工作:模式匹配与模式融合.模式匹配采用本体的"Bridge(桥接)"效应建立不同接口模式间的属性映射关系,以准确发现不同接口属性间的语义关联.模式融合根据模式匹配的结果,合并DeepWeb数据库查询接口集合中表示同一语义的属性,并尽可能地保持该领域查询接口的结构特征和属性顺序,以获得集成查询接口.通过实验分析,基于本体的DeepWeb查询接口集成方法不仅简化了模式匹配的复杂过程,而且很大程度上提高了模式集成的精度.因此,基于本体的Deep Web查询接口集成方法是高效可行的.     

Object-oriented query language access to relational databases: A semantic framework for query translation

This research investigates and approach to query processing in a multidatabase system that uses an objectoriented model to capture the semantics of other data models. The object-oriented model is used to construct a global schema, defining an integrated view of the different schemas in the environment. The model is also used as a self-describing model to build a meta-database for storing information about the global schema. A unique aspect of this work is that the object-oriented model is used to describe the different data models of the multidatabase environment, thereby extending the meta database with semantic information about the local schemas. With the global and local schemas all represented in an object-oriented form, structural mappings between the global schema and each local schema are then easily supported. An object algebra then provides a query language for expressing global queries, using the structural mappings to translate object algebra queries into SQL queries over local relational schema. The advantage of using an object algebra is that the object-oriented database can be viewed as a blackboard for temporary storage of local data and for establishing relationships between different databases. The object algebra can be used to directly retrieve temporarily-stored data from the object-oriented database or to transparently retrieve data from local sources using the translation process described in this paper.     

多XML数据源的语义集成与查询处理

提出一种多XML数据源的语义集成和查询处理的途径,通过一定步骤将各个局部DTD模式集成为全局模式,同时生成全局模式到局部模式的映射。在查询处理中,查询被表示成查询树的形式,引入了补查询和连接子等概念,给出了查询分解和执行的具体算法,并首次提出并分析了XML集成环境下产生不确定查询结果的情况。     

基于《知网》的中文Deep Web模式匹配算法研究

随着数据库在Internet中的应用日益广泛,Deep Web集成（即Web数据库集成）成为当前信息领域的研究热点,模式匹配是Deep Web查询接口集成中的一个关键问题。目前大多数这方面的研究都是基于英文的,针对这种情况,探讨了中文Deep Web查询接口的模式匹配方法,并提出了一种基于《知网》、面向中文语义的模式匹配算法,并利用属性在查询接口上的相对位置信息解决语义冲突。手工收集查询表单对算法进行验证,实验表明该方法能使得接口之间属性匹配的正确率达到90 %以上。     

A research agenda for query processing in large-scale peer data management systems

Peer Data Management Systems (Pdms) are a novel, useful, but challenging paradigm for distributed data management and query processing. Conventional integrated information systems have a hierarchical structure with an integration component that manages a global schema and distributes queries against this schema to the underlying data sources. Pdms are a natural extension to this architecture by allowing each participating system (peer) to act both as a data source and as an integrator. Peers are interconnected by schema mappings, which guide the rewriting of queries between the heterogeneous schemas, and thus form a P2P (peer-to-peer)-like network.Despite several years of research, the development of efficient Pdms still holds many challenges. In this article we first survey the state of the art on peer data management: We classify Pdms by characteristics concerning their system model, their semantics, their query planning schemes, and their maintenance. Then we systematically examine open research directions in each of those areas. In particular, we observe that research results from both the domain of P2P systems and of conventional distributed data management can have an impact on the development of Pdms.     

基于时态变量对象关系模型及代数运算

时态数据处理多是基于关系数据库平台,时态数据库模型也以时态关系数据模型为主.关系数据模型难以处理具有复杂类型的数据对象,而面向对象数据模型还缺乏商业化应用平台.现有关系数据库平台大多增加了面向对象基本功能,形成了对象关系数据库系统,因此将对象关系数据模型进行时态扩充就显得十分必要和具有可行性.首先在现有时态关系数据模型基础上,提出了一种基于对象关系双时态数据模型,而这种数据模型适合于在现有数据库平台上实现;其次,在该模型框架内,讨论了时态对象关系模式与时态关系模式相互间的联系与转换,这也是由时态关系扩充到对象关系的基本要求;再次,分析了时态模型中时态变量复杂语义和相应绑定算法,这是时态数据库能够有效运行的基本课题之一;最后,研究了基于时态变量复杂语义的时态对象关系数据操作代数,从而为时态对象关系模式的查询进行了必要的理论探讨.     

Semantic integration in Xyleme: a uniform tree-based approach

Xyleme is a huge warehouse integrating XML data of the Web. Xyleme considers a simple data model with data trees and tree types for describing the data sources, and a simple query language based on tree queries with boolean conditions. The main components of the data model are a mediated schema modeled by an abstract tree type, as a view of a set of tree types associated with actual data trees, called concrete tree types, and a mapping expressing the connection between the mediated schema and the concrete tree types. The first contribution of this paper is formal: we provide a declarative model-theoretic semantics for Xyleme tree queries, a way of checking tree query containment, and a characterization of tree queries as a composition of branch queries. The other contributions are algorithmic and handle the potentially huge size of the mapping relation which is a crucial issue for semantic integration and query evaluation in Xyleme. First, we propose a method for pre-evaluating queries at compile time by storing some specific meta-information about the mapping into map translation tables. These map translation tables summarize the set of all the branch queries that can be generated from the mediated schema and the set of all the mappings. Then, we propose different operators and strategies for relaxing queries which, having an empty map translation table, will have no answer if they are evaluated against the data. Finally, we present a method for semi-automatically generating the mapping relation.     

TIGUKAT: A uniform behavioral objectbase management system

We describe the TIGUKAT objectbase management system, which is under development at the Laboratory for Database Systems Research at the University of Alberta. TIGUKAT has a novel object model, whose identifying characteristics include a purely behavioral semantics and a uniform approach to objects. Everything in the system, including types, classes, collections, behaviors, and functions, as well as meta-information, is a first-class object with well-defined behavior. In this way, the model abstracts everything, including traditional structural notions such as instance variables, method implementation, and schema definition, into a uniform semantics of behaviors on objects. Our emphasis in this article is on the object model, its implementation, the persistence model, and the query language. We also (briefly) present other database management functions that are under development such as the query optimizer, the version control system, and the transaction manager.Bell Northem Research     

基于模式映射的查询计划生成算法

因特网的迅速发展使得多数据源综合集成日益重要.但是,不同数据源之间数据结构和语义的异构性导致数据集成是相当困难的.本文提出了一种基于模式映射的查询计划生成算法.该算法在正确定义映射规则的前提下,根据不同的查询条件和不同的数据源模式,自动构造查询计划,并保证结果数据满足目标模式结构与引用完整性要求.