OO代数——一个面向对象的数据库的基本查询模型

OO ALGEBRA A PRELIMINARY QUERY MODEL FOR OBJECT-ORIENTED DATABASES

本文提出了一个面向对象的数据库系统的基本查询模型——ＯＯ代数，它具有关系代数相似的形式，具有封闭性和远比关系代数强得多的表达能力。文中首先给出了面向对象的数据库系统的数据结构的一种形式化描述－ＯＳＧ，然后ＯＯ代数的五种基本运算：并、差、类间连接、类内选择及广义投影被一一定义。

A preliminary query model for Object Orientd Databas system,called OO algedra,is proposed in this paper,which has a similar format as relational algebra,is self closed and far more powerful than relational algebra.First,a formal description of data structure of Object orientd data model,which is calld OSG,is presented;then,each of the five elementary operations of OO Algebra:Union,Substraction,Join between two classes,Selection within a class and generalized projection,is in turn defined and implementation methods of these operation using relational operations are also given.