知识库查询的固有低效性

The Inherent Inefficiency of KB Query Evaluation

1．引言 知识库研究的重要内容之一是查询优化技术的研究。从七十年代后期开始,经过八十年代,到目前为止,知识库查询优化方面已经取得了大量研究成果,开发了许多有效的查询优化算法。例如：Semi-Naive求值[1]、Magic-Set重写技术和Counting方法[2,3]等等。这些技术的应用,大大提高了知识库的查询效率。尽管如此,知识库的查询效率仍不能令人满意,这是知识库系统不能实用的主要原因之一。

This paper introduces the concepts of knowledge-base system and the scale of knowledge-base's application, analyses the method of knowledge-base query evaluation, and presents several obstacles during this evaluation. All of them cannot be well treated by current hardware techniques and software methods. Therefore inefficiency of knowledge-base queries are inherent today. Finally several research directions of the query optimization of knowledge-base systems are given.