实时数据库的主动机制研究与实现

Research and Implementation on Active Mechanism in Real Time Databases

主动机制是实时数据库管理系统 (DBMS)的一个重要功能。在主动机制的基础上 ,实时DBMS能够根据数据库中某些数据及环境的变化 ,主动地作出一定的反应 ,执行预先设计的动作 ,而不仅仅是被动地执行用户的命令。文中主要介绍一个实时 DBMS的主动子系统 ,采用事件 -条件 -动作的规则来实现其主动功能 ;讨论了规则的表示和存储结构 ,规则子系统的系统结构及与 DBMS的联系 ;并详细介绍了条件评价器、规则检索优化、规则冲突。

The active mechanism is an important function of real time databases. Based on the active mechanism, real time DBMS can actively execute some actions defined in advanced when the data in database or the environment are changed. This paper introduces an active subsystem of real time DBMS, which uses the rules of the event condition action to implement its active function. The paper discusses the representation and storage structure of the rules, the subsystem structure and the relation between the subsystem, and DBMS presents emphatically the methods and the techniques of dealing with and implementing the condition evaluator, search optimization of rules, rule conflict, and recursive trigger of rules.