[show abstract][hide abstract] ABSTRACT: In this paper, the concept of a granulation order is proposed in an information system. The positive approximation of a set
under a granulation order is defined. Some properties of positive approximation are obtained. For a set of the universe in
an information system, its approximation accuracy is monotonously increasing under a granulation order. This means that a
proper family of granulations can be chosen for a target concept approximation according to the user requirements. An algorithm
based on positive approximation is designed for decision rule mining, and its application is illustrated by an example.