The primitive notion in rough set theory is a pair of upper and lower approximation operators induced by the basic structure, an approximation space, consisting of a universe of discourse and a binary relation on it. 粗糙集理论的核心算子是从近似空间导出的一对非数值型算子-上近似算子与下近似算子,这一对近似算子是整个粗糙集理论与应用的基础。
Totem culture is a very complicated cultural phenomenon which originated in primitive time. Totem notion, totem taboo and totem art are the main elements which constituted totem culture. 图腾文化是一种产生于原始时代的十分奇特复杂的文化现象,图腾观念、图腾禁忌及图腾艺术等构成图腾文化的主要元素。