Fuzzy ideals in BCI-algebras

Abstract The aim of this paper is to introduce the notions of fuzzy BCI-positive implicative ideals and fuzzy BCI-implicative ideals of BCI-algebras and to investigate their properties. We give several characterizations of fuzzy BCI-positive implicative ideals and fuzzy BCI-implicative ideals. The extension theorems of fuzzy BCI-positive implicative ideals and fuzzy BCI-implicative ideals are obtained. We discuss the relations among various fuzzy ideals and show that a fuzzy set μ of a BCI-algebra is fuzzy BCI-implicative ideal if and only if μ is both fuzzy BCI-positive implicative ideal and fuzzy BCI-commutative ideal. Finally, we characterize implicative (positive implicative) BCI-algebras via fuzzy BCI-implicative (fuzzy BCI-positive implicative) ideals.