多媒体对象查询语言及其查询处理

文章研究了多媒体数据库的查询需求,提出结构化的多媒体对象查询语言MOQL(multi-media object query language).它能够支持基于类型、结构特征、同步关系、时态关系和内容信息的多媒体查询.以DB2数据库为存储机制,定义了一组代数算子和变换规则,利用它们可以将用户定义的MOQL查询变换为代数表达式,进行代数优化,并将代数查询表达式转换为能够在DB2数据库上运行的DB2SQL和C++查询过程.     

基于BCDM的双时态关系代数

双时态概念数据模型BCDM是一种重要的时态数据库模型，基于BCDM模型，建立了一种双时态关系代数．首先，对时态数据库事务时间和有效时间进行规范化的定义，给出BCDM中时间元素的规范化定义和演算描述；而后，定义时态映射，用以描述BCDM中的双时态元组，并形式描述时态映射的演算；最后，用时态映射定义的元组对双时态关系进行定义，并由此给出双时态关系代数运算的形式化描述．     

基于二阶基调的时空查询代数形式化定义

提出了一种基于对象关系数据库和中间件技术的时空数据库系统实现与查询处理框架，着重论述了其中的时空查询代数。引入了二阶基调用于时空查询代数的形式化定义，给出了时宅数据库的逻辑结构定义、类型系统定义以及查询操作定义。     

数据库查询的优化策略探讨

本文从数据库的物理优化、代数优化和规则优化等不同角度,探讨了数据库查询的优化策略,提出了一些查询优化的具体方法.     

演绎面向对象数据库语言中的方法研究

方法和方法继承是面向对象的核心概念.本文介绍了约束演绎对象语言CDOL(constraint deductive object language)中方法的概念及定义，方法是作为规则定义的，它既可作为对象的接口，又可用来实现计算的抽象与共享，方法的继承和多态是通过类型机制和合一机制来实现的.     

超文档的数据库模型

用数据库技术实现超文档的管理是数据库领域一个新的研究方向,文章介绍了这一研究方向的新进展.Alberto和George使用关系型数据库管理超文档中的链接,对查询语言SQL进行扩展,提出查询语言WebSQL.Serge Abiteboul使用面向对象数据库表示超文档,对查询语言OQL进行扩展,提出OQL－doc.前者没有提出如何用数据模型表示超文档,后者则没考虑超文档中的链接,为此该文提出进一步的解决方法,将链接用对象表示,引入链接距离、文档树、文档的n层链接树概念,并以例子说明这些方法的使用.     

数据库查询的优化策略探讨

本文从数据库的物理优化、代数优化和规则优化等不同角度,探讨了数据库查询的优化策略,提出了一些查询优化的具体方法。     

面向对象数据库中查询代价的估算

好的查询优化器都是基于代价的，因此查询代价的估算是数据库查询优化中一项不可缺少的工作。文中在联系代数的基础上，综合考虑了对象聚集，索引等因素，给出了面向对象数据库中查询代价的一种估算方法。     

数据库汉语自然语言查询界面NLCQI的设计和实现

本文介绍了我们所设计和研制的基于受限汉语的数据库自然语言查询界面ＮＬＣＱＩ，它运用Ｅ－Ｒ语法，语义结构的汉语查询模型，建立一种以类关系代数语句模板为规则的中间语言ＭＱＬ的转换机制，实现了从ＭＱＬ到ＳＱＬ的直接转换，本文详细地介绍了该系统的结构原理以及主要的转换算法。     

对象类型的等价代换与规范化

本文讨论了面向对象数据库模式中对象类型的规范化，基于对象集合的等价提出了类型的一种范式、给出了将类型转换为范式的规则、并且证明了范式的唯一性及转换规则的完备性，本文工作在面向对象数据库设计标准化方面迈出了一步。     

ODMG'93的ODL、OQL语言到F-logic程序的转换

为了分析ＯＤＭＧ’９３数据对象模型的语义,本文给出了一套转换规则,将ＯＤＭＧ’９３的对象定义语言ＯＤＬ、对象查询语言ＯＱＬ转换到Ｆ－ｌｏｇｉｃ程序,并结合面向对象数据库管理系统Ｏ２,通过具体的实例陈述了该转换规则是完全的。     

How to Comprehend Queries Functionally

Compilers and optimizers for declarative query languages use some form of intermediate language to represent user-level queries. The advent of compositional query languages for orthogonal type systems (e.g., OQL) calls for internal query representations beyond extensions of relational algebra. This work adopts a view of query processing which is greatly influenced by ideas from the functional programming domain. A uniform formal framework is presented which covers all query translation phases, including user-level query language compilation, query optimization, and execution plan generation. We pursue the type-based design—based on initial algebras—of a core functional language which is then developed into an intermediate representation that fits the needs of advanced query processing. Based on the principle of structural recursion we extend the language by monad comprehensions (which provide us with a calculus-style sublanguage that proves to be useful during the optimization of nested queries) and combinators (abstractions of the query operators implemented by the underlying target query engine). Due to its functional nature, the language is susceptible to program transformation techniques that were developed by the functional programming as well as the functional data model communities. We show how database query processing can substantially benefit from these techniques.     

Association algebra: a mathematical foundation for object-orienteddatabases

The application of the object-oriented (O-O) paradigm in the database management field has gained much attention in recent years. Several experimental and commercial O-O database management systems have become available. However, the existing O-O DBMSs still lack a solid mathematical foundation for the manipulation of O-O databases, the optimization of queries, and the design and selection of storage structures for supporting O-O database manipulations. This paper presents an association algebra (A-algebra) to serve as a mathematical foundation for processing O-O databases, which is analogous to the relational algebra used for processing relational databases. In this algebra, objects and their associations in an O-O database are uniformly represented by association patterns which are manipulated by a number of operators to produce other association patterns. Different from the relational algebra, in which set operations operate on relations with union-compatible structures, the A-algebra operators can operate on association patterns of homogeneous and heterogeneous structures. Different from the traditional record-based relational processing, the A-algebra allows very complex patterns of object associations to be directly manipulated. The pattern-based query formulation and the A-algebra operators are described. Some mathematical properties of the algebraic operators are presented together with their application in query decomposition and optimization. The completeness of the A-algebra is also defined and proven. The A-algebra has been used as the basis for the design and implementation of an object-oriented query language, OQL, which is the query language used in a prototype Knowledge Base Management System OSAM*.KBMS     

Query languages for relational multidatabases

With the existence of many autonomous databases widely accessible through computer networks, users will require the capability to jointly manipulate data in different databases. A multidatabase system provides such a capability through a multidatabase manipulation language, such as MSQL. We propose a theoretical foundation for such languages by presenting a multirelational algebra and calculus based on the relational algebra and calculus. The proposal is illustrated by various queries on an example multidatabase. It is shown that properties of the multirelational algebra may be used for optimization and that every multirelational algebra query can be expressed as a multirelational calculus query. The connection between the multirelational languages and MSQL, the multidatabase version of SQL, is also investigated.     

Database query languages and functional logic programming

Functional logic programming is a paradigm which integrates functional and logic programming. It is based on the use of rewriting rules for defining programs, and rewriting for goal solving. In this context, goals, usually, consist of equality (and, sometimes, inequality) constraints, which are solved in order to obtain answers, represented by means of substitutions. On the other hand, database programming languages involve a data model, a data definition language and, finally, a query language against the data defined according to the data model. To use functional logic programming as a database programming language, (1) we will propose a data model involving the main features adopted from functional logic programming (for instance, handling of partial and infinite data), (2) we will use conditional rewriting rules as data definition language, and finally, (3) we will deal with equality and inequality constraints as query language. Moreover, as most database systems, (4) we will propose an extended relational calculus and algebra, which can be used as alternative query languages in this framework. Finally, (5) we will prove that three alternative query languages are equivalent.     

Foundations for object-oriented query processing

A minimal framework for an object-oriented query language standard should (1) include a formal definition of a high-level data model and the syntax and semantics of associated query languages, (2) provide the functionality of relational query languages, and (3) support proofs of correctness of transformations for logical query optimization. In this paper, a high-level conceptual model for object-oriented query processing is discussed; the model includes widely-used structural abstractions such as the isa relationship, associations (properties) between complex objects and complex objects/values, and inheritance of properties. A formal, algebraic query language for the model, inspired by relational algebra, is presented. Operators of the algebra allow queries based on values, queries that manipulate entire objects, and queries that construct new objects from existing objects/values. All queries retain connections to existing database objects, providing logical access paths to data. Each query result is a class, so the algebra has the closure property. The intensional and extensional results of query operators are summarized. Two forms of logical query optimization supported by the query algebra are outlined: algebraic transformations and classifier-based optimizations (optimizations which employ inclusion and exclusion dependencies between classes).     

Providing views and closure for the object data management group object model

The object data management group (ODMG) object model offers a standard for object-oriented database designers, while attempting to address some issues of interoperability. This research is focused on the viability of using the ODMG data model as a canonical data model in a multidatabase environment, and where weaknesses are identified we have proposed amendments to enable the model to suit the specific needs of this type of distributed database system. This paper describes our efforts to extend its relational style algebra, and to provide query closure and a viewing mechanism for object query language to construct multidatabase schemas.     

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.