@ARTICLE { Rsds3601,
author = {Yichen, Ma and Deyu, Li}, 
title = {Invariant characters of information systems under some homomorphisms}, 
journal = {Information Sciences: An International Journal}, 
number = 	{(no. 1-4)}, 
volume = 129, 
pages = {211-220}, 
publisher = {Elsevier Science Inc.}, 
address = {Amsterdam, The Netherlands}, 
month = {November}, 
year = 2000, 
issn = {0020-0255}, 
abstract = {An information system is one of the very important mathematical models in the field of artificial intelligence. The notion of an information system homomorphism as a kind of tool to study the relation between two information systems was introduced in J.W. Grzymala-Busse (Algebraic properties of knowledge representation systems, in: Proceedings of the ACM SIGART International Symposium on Methodologies for Intelligent Systems, Knoxville, 1986, pp. 432-440). In this paper, some invariant characters of an information system under a homomorphism are discussed.}, 
keywords = {rough set theory (RST), indiscernibility relation, information systems, superfluous attribute, information system homomorphism, }, 
}