Rough set; covering approximation subspace; covering approximation operator; definable; outer definable; inner definable
) be a subspace of a covering approximation space (U
) and X⊂U'
. In this paper, we show that
) has Property Multiplication. Furthermore, some connections between outer (resp. inner) definable subsets in (U
) and outer (resp. inner) definable subsets in (U'
) are established. These results answer a question on covering approximation subspace posed by J. Li, and are helpful to obtain further applications of Pawlak rough set theory in pattern recognition and artificial intelligence.
Zhangjiagang college, Jiangsu University of Science and Technology,
Zhangjiagang 215600, P. R. China
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