Date Added: Jun 2012
This paper reviews and compares theories of level II fuzzy sets and type II fuzzy sets. Two approaches for the usefulness of level II fuzzy sets are reviewed one is in database modeling while other is in GIS. Type II fuzzy sets under set theoretic view seem to be closely related to level II fuzzy sets, but linguistically they deal with different types of variables in database modeling. Theories of level II fuzzy sets and type II fuzzy sets are generalizations of fuzzy set theory for modeling higher order of uncertainty. Real world problem involve many kinds of imperfections in the data.