At present, the accuracy of formal concept based granule description with undetermined values still has plenty of room for improvement. For this purpose, this paper presents a granule description method for uncertain data in a three-way epistemic perspective. Specifically, we resort to a kind of three-way epistemic model, i.e., three-way concepts. Firstly, three-way concepts are investigated by their stabilities in formal contexts with undetermined values. Then, an incomplete granule description method is proposed by using a three-way epistemic perspective. Finally, the accuracy and efficiency of the proposed method are compared with the classical epistemic perspective based method. It can be shown that the former can obtain a higher description accuracy. Moreover, if basic granules are taken as priori knowledge, both the number and acquisition time of basic granules under the framework of three-way epistemic perspective are significantly more than those under the framework of formal concepts. However, once the prior knowledge is obtained, there is no significant difference in incomplete granule description in terms of time consumption.
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