Integrating relational and object-oriented database systems using a metaclass concept

This paper presents a specific approach of integrating a relational database system into a federated database system. The underlying database integration process consist of three steps: first, the external database systems have to be connected to the integrated database system environment and the external data models have to be mapped into a canonical data model. This step is often called syntactic transformation including structural enrichment and leads to component schemas for each external DBMS. Second, the resulting schemas from the first step are used to construct export schemas which are then integrated into global, individual schemas or views in the third step. In this paper we focus on the first step for relational databases, i.e., the connection of a relational database system and the mapping of the relational model into a canonical data model. We take POSTGRES as the relational database system and the object-oriented federated database system VODAK as the integration platform which provides the open, object-oriented data model as the canonical data model for the integration. We show different variations of mapping the relational model. By exploiting the metaclass concept provided by VML, the modelling language of VODAK, we show how to tailor VML such that the canonical data model meets the requirements of integrating POSTGRES into the global database system VODAK in an efficient way.     

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.     

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.     

Migration in object-oriented database systems—A practical approach

Object-oriented database systems are designed to meet the requirements of advanced database applications such as computer-integrated manufacturing. These requirements may evolve in the course of time and may require the migration of the database application from one object-oriented database system to another. Traditional migration approaches for relational database systems fail when applied to object-oriented database systems. The goal of this paper is to fill this gap. The paper describes a framework for the migration of object-oriented database applications. Our approach is based on a detailed analysis of the involved database systems, of the application's database requirements, and of the resources available for the database migration. We illustrate our framework by means of a case study, which is migrating an electronic planning board system from the object-oriented database system ONTOS to ObjectStore.     

Redesigning, implementing and integrating Escherichia coli genome software tools with an object-oriented database system.

This paper reports our exploratory work to redesign, implement and integrate a collection of genome software tools with an object-oriented database system. Our software tools deal with genome data from Escherichia coli K-12, a bacterium that has been studied intensively and provides richer data sets than any other living organism. The object-oriented DBMS used for the integration is ONTOS, a commercial object-oriented system from Ontologic Inc. This redesign and implementation task was performed in two steps. First, C programs were converted into C++, and then the C++ version programs were modified and integrated with an object-oriented modeling of the data to form an ONTOS database application. The first step helps us develop a conceptual view for a DBMS-independent object-oriented construct. The second step elucidates what additional DBMS-dependent modification steps are needed to provide persistency to the objects. Examples are included to illustrate steps of the redesign and implementation. Overall, the outcome of this project demonstrates that programs and data can be successfully integrated with an object-oriented database, while providing the objects with persistency and shareability. This paper includes discussions using concrete examples on what advantage the object-oriented database approach provides over the relational database approach.     

一种新颖的测控数据库

本文对开发面向测控领域的实时数据库管理系统的必要性进行了论述,并设计了一种新颖的基于关系模型的实时数据库管理系统(RDBMS)。该系统提供实时数据库结构化查询语言(RDBSQL)以进行实时数据库查询操作,提供实时数据库调用接口(RDBⅡ)以开发应用程序。     

面向对象数据库管理技术在IDSS中的应用

以一个智能决策支持中的专用面向对象数据管理系统OOSM为例，提出一套以提供开发支持为目的的面向对象数据管理模式，OOSM对象模型的定义充分借鉴了面向对象编程语言C＋＋的特性，永久性存储是采和了关系数据库系统与文件系统相结合的方式。介绍了OOSM提供的对象实例查询与操纵语言，这种语言是通过向客户提供通用模板代码的方式实现的。文中最后以作战方案对象为例，描述了上述模式的应用。     

基于DAO模式的持久模型的研究与设计①

开发一个同时使用面向对象技术和关系型数据库技术的项目是一件困难的事情。提出了一个基于DAO模式的数据持久模型,通过可变机制将底层的数据访问独立封装起来,使得对象模型与关系数据库之间具有无关性。同时通过缓冲等机制大大提高了数据访问的效率。     

基于DAO模式的持久模型的研究与设计①

开发一个同时使用面向对象技术和关系型数据库技术的项目是一件困难的事情。提出了一个基于DAO模式的数据持久模型,通过可变机制将底层的数据访问独立封装起来,使得对象模型与关系数据库之间具有无关性。同时通过缓冲等机制大大提高了数据访问的效率。     

Issues in query model design in object-oriented database systems

The provision of a powerful query system, including a declarative query language and the systems support for efficiently processing queries is essential for the success of object-oriented database technology. Designing a query system involves making a large number of decisions, further complicated by the lack of a universally accepted object-oriented object data model. In this paper, object data model and query model design decisions are enumerated, alternatives are identified, and the tradeoffs are specified.     

ArchIS: an XML-based approach to transaction-time temporal database systems

Effective support for temporal applications by database systems represents an important technical objective that is difficult to achieve since it requires an integrated solution for several problems, including (i) expressive temporal representations and data models, (ii) powerful languages for temporal queries and snapshot queries, (iii) indexing, clustering and query optimization techniques for managing temporal information efficiently, and (iv) architectures that bring together the different pieces of enabling technology into a robust system. In this paper, we present the ArchIS system that achieves these objectives by supporting a temporally grouped data model on top of RDBMS. ArchIS’ architecture uses (a) XML to support temporally grouped (virtual) representations of the database history, (b) XQuery to express powerful temporal queries on such views, (c) temporal clustering and indexing techniques for managing the actual historical data in a relational database, and (d) SQL/XML for executing the queries on the XML views as equivalent queries on the relational database. The performance studies presented in the paper show that ArchIS is quite effective at storing and retrieving under complex query conditions the transaction-time history of relational databases, and can also assure excellent storage efficiency by providing compression as an option. This approach achieves full-functionality transaction-time databases without requiring temporal extensions in XML or database standards, and provides critical support to emerging application areas such as RFID.     

对象模型向关系数据库模式映射的策略及其应用

面向对象的关系数据库设计是面向对象软件工程的一个环节,而对象模型向关系数据库模式的映射是面向对象关系数据库设计的核心。结合油气储运网络管理系统的一期工程实践,对对象模型向关系数据库模式映射的策略进行了讨论。应用结果表明,应用系统采用面向对象的分析和设计方法,结合传统的关系数据库模型可加快软件开发进程,具有较好的经济性和可行性。     

基于面向对象空间数据库的三维地景可视化研究

该文设计了一个基于面向对象空间数据库的三维地景(terrain)可视化系统,并依据人们对地图的理解角度提出了面向对象的四级数据模型,研究了场景生成技术,开发了底层的面向对象的空间数据库。系统具有良好的通用性和可扩展性,在飞行模拟、实时动态仿真及虚拟现实等领域有较广泛的应用前景。     

Embedding deductive capabilities in relational database systems

The basic idea of our work is to include deductive capabilities in a relational database system by fully using the operands of relational algebra and without using any theorem prover. We present a deductive database system where the user can formulate deduction laws as logical formulas, but which works on an underlying relational database system by fully using the data manipulation routines of such a system. Generally, it is not possible to express the deduction laws by means of expressions of relational algebra (see Ref. 1). In our system, a relational algebra expression is associated with every database deduction law. The result of its evaluation (with respect to an underlying database) is the set of all database entries that can be deduced from the database by applying the respective law once (Theorem 1). By successively applying all these relational expressions for all the database deduction laws it is possible to generate the whole extensional database (i.e. all tuples deducible from the database).     

面向对象数据库（OODB）与关系数据库（RDB）之比较研究

面向对象数据库至今还没有权威的定义，为把握与了解面向对象数据库的实质，我们采用比较研究法，首先从数据库发展史来剖析面向对象数据库与关系数据库之间的联系与差异。然后在功能，性能上分别讨论各自的亿势与劣势，阐面向对象数据库的本质与特征。     

SEEKER:基于关键词的关系数据库信息检索

传统上,SQL是存取关系数据库中数据的主要界面.但是,对于没有经验的用户来说,学习复杂的SQL语法是一件困难的事情.实现基于关键词的关系数据库信息检索,将使用户不需要任何SQL语言和底层数据库模式的知识,用搜索引擎的方式来获取数据库中的相关数据.描述了一个基于关键词的关系数据库信息检索系统SEEKER的设计和实现.现有的关系数据库关键词查询系统只能检索关系数据库中的文本属性,而SEEKER还可以检索数据库元数据以及数字属性.并且,SEEKER采用了更合理的排序公式,支持Top-k查询.实验结果显示,SEEKER具有良好的查询性能.     

基于OO技术的关系数据库设计

就面向对象模型的关系数据库存储进行了讨论，并以“设备售后服务系统”为例，详细论述了从面向对象的设计类图向关系数据库的映射方法。     

Design and Implementation of the ROL Deductive Object-Oriented Database System

ROL is a deductive object-oriented database system that has been implemented at the University of Regina. It provides a uniform rule-based declarative language for defining, manipulating and querying databases, which integrates important features of both deductive databases and object-oriented databases. It supports object identity, complex objects, classes, class hierarchies, multiple inheritance with overriding and blocking, and schema definition. It also supports structured values such as functor objects and sets, treating them as first class citizens, and providing powerful mechanisms for representing both partial and complete information about sets. This paper describes its design and implementation. An important novel feature of the implementation is that it combines top-down and bottom-up evaluation strategies and automatically selects a strategy based on the nature of the query and data in the database.     

统一多维数据模型的后关系数据库体系结构

随着面向对象编程技术的推广和Web技术的广泛应用,迫切需要在数据库领域提供对这些新技术的高效支持,而传统的关系数据库由于其本身的局限性在这些方面表现不佳。针对这一问题,并结合对象数据库及XML数据库的发展现状,提出了一种基于应用驱动的多接口混合型后关系数据库体系结构的概念模型,并在理论上加以验证。