关键词: 数据库，关系，属性，描述逻辑，概念

Abstract: Two description logics for relations in databases were given in our work. On the one hand, in one description logic, a relation can be represented as a know-ledge base and a model of the knowledge base, and any model of the knowledge base has a sub-model which is isomorphic to the relation; on the other hand, in another description logic, a relation can be represented as a knowledge base and a model of the knowledge base so that any model of the knowledge base is isomorphic to the relation.

Key words: Database, Relations, Attributes, Description logics, Concepts