@INPROCEEDINGS { Rsds205,
author = {Bonikowski, Zbigniew}, 
title = {Algebraic Structures of Rough Sets in Representative Approximation Spaces}, 
booktitle = {Electronic Notes in Theoretical Computer Science}, 
volume = 82, 
pages = {52-63}, 
publisher = {Springer-Verlag}, 
address = {Heidelberg - Berlin, Germany}, 
year = 2003, 
editor = {Skowron, Andrzej and Szczuka, Marcin}, 
abstract = {In this paper a generalized notion of an approximation space is considered. By an approximation space we mean an ordered pair (U,C), where U is a finite nonempty set and C is a covering of U. According to connections between rough sets and concepts we define two types of approximation operations. Hence we obtain two families of rough sets. We show that these families form lattices in special types of representative approximation spaces. The operations on rough sets defined in the above lattices are analogous to classical operations on sets.}, 
keywords = {rough sets, approximation operations, }, 
}