Affiliations: Department of Electrical Engineering and Computer
Science, University of Kansas, Lawrence, KS 66045, USA. jerzy@ku.edu | Department of Computer Science, University of Rzeszow,
35–310 Rzeszow, Poland. wrzasa@univ.rzeszow.pl
Note: [] Address for correspondence: Department of Electrical Engineering
and Computer Science, University of Kansas, Lawrence, KS 66045, USA
Abstract: In this paper we discuss approximation spaces that are useful for
studying local lower and upper approximations. Set definability and properties
of the approximation space, including best approximations, are considered as
well. Finding best approximations is a NP-hard problem. Finally, we present
LEM2-like algorithms for determining local lower and upper coverings for a
given incomplete data set. Lower and upper approximations, associated with
these coverings, are sub-optimal.
