一个新的面向对象数据库系统的动态数据模型

A New Dynamic Data Model for Object-Oriented Database Systems

现有的 OODBMS(object- oriented database management systems)的数据模型基本上可以分为两类 :传统的强类型和非传统的弱类型 .前者的特征是所有具有同样结构 (模式 )和行为 (方法 )的对象组成一个类 ,对象的含义由对象所属类的模式解释 ,故类的定义必须先于其对象的定义 ;后者的特征是“无模式”,即对象是“自我描述”的 ,因此无须为对象预先定义模式 .指出了这两类模型的主要优缺点 ,并证实 :为了充分适应有效而灵活的动态对象操作 ,有必要在传统的强类型模型和非传统的弱类型模型之间寻求某种折衷 .为此 ,提出了一个基于概念聚类机制 (conceptual clustering mechanism,简称 CCM)的数据模型 .这种新的动态模型已成功地应用于一个面向对象的 VDBMS(video database management system)

The current data models used in OODBMS (object oriented database management systems) are basically divided into two categories: traditional ‘type strong’ and non traditional ‘type weak’. The feature of the former is that the objects sharing the same structure (schema) and behaviors (methods) are grouped into a class. The schema of class to which the objects belong interprets the meaning of the objects. Therefore a class must be predefined before its objects are defined. The latter is characterized by schema less, i.e., the meaning of the objects is ‘self describing’, and hence the schema need not to be defined in advance for the objects. In this paper, after outlining the main advantages and disadvantages of these two kinds of models, the authors prove that it is necessary to find some tradeoffs between traditional ‘type strong’ data models and non traditional ‘type weak’ ones in order to adequately accommodate the efficient and flexible manipulation of dynamic objects. For this reason, a novel dynamic data model is proposed based on CCM (conceptual clustering mechanism) which has been successfully used for the development of an object oriented VDBMS (video database management system).