As traditional description logic systems are not good at representing uncertain (or vague)knowledge, this paper introduces lower approximation and upper approximation which are based on the rough set semantics to description logic systems, and extends the traditional description logic in a simple way. It introduces the concept of rough description logic, in the systems of which we can use appropriate sub-concept and super-concept to express some vague knowledge. This paper focuses on the rough extension of the description logic ALC and introduces the syntax, semantics and related reasoning problems of the rough description logic RALC obtained after extension, and then discusses the basic idea of modeling imprecise concepts using the rough description logic. Finally, the paper presents a reasoning algorithm of the satisfiability problem of RALC. This task can make formal descriptions and reasoning of uncertain knowledge in the description logic more convenient.%由于传统的描述逻辑系统不适于表示不确定的、模糊的知识,本文将基于粗糙集语义的下近似和上近似引入描述逻辑系统中,使用一种简单的方法将传统描述逻辑进行扩展,介绍了粗糙描述逻辑的概念,在粗糙描述逻辑系统中我们可以使用适当的子概念和超概念来对某些模糊的知识进行约束表示.本文主要讨论描述逻辑ALC的粗糙扩展,介绍扩展后所得到的粗糙描述逻辑RALC的语法、语义和相关推理问题,探讨了使用粗糙描述逻辑来对不精确概念进行建模的基本思想,最后提出了一个RALC的可满足性问题的推理算法.本文的工作可以使得在描述逻辑中对不确定的知识进行形式化描述和推理更加方便.
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