【摘要】 在面向对象数据库中，需有效支持关系操作，已成为大多数研究人员的共识，但该问题仍未得到妥善解决，主要原因是由于面向对象模型缺乏像关系模型那样坚实的理论基础．为服务于此目的，在Ｓ．Ｙ．Ｗ．Ｓｕ等人提出的基于无向图的联系代数的基础上，本文提出了基于有向图的联系代数，并给出了一个优化联系代数表达式的算法．本文所提出的改进较其原形式能更精确地反映面向对象模型的实质，更有利于对象的查询处理与优化．更多还原

【Abstract】 This paper presents directed graph based association algebra which is an important improvement of nondirected graph based association algebra worked outby S. Y. W. Su et al,and gives an algorithm for optimizing association algebraic expressions. Directed graph based association algebra can reflect more precisely theintrinsic quality of object-oriented models and has more advantage over query processing and optimization of objects than its nondirected graph based counterpart.更多还原