A characterization of regular, intra-regular, left quasi-regular and   semisimple hypersemigroups in terms of fuzzy sets
  We prove that an hypersemigroup $H$ is regular if and only, for any fuzzy subset $f$ of $H$, we have $f\preceq f\circ 1\circ f$ and it is intra-regular if and only if, for any fuzzy subset $f$ of $H$, we have $f\preceq 1\circ f\circ f\circ 1$. An hypersemigroup $H$ is left (resp. right) quasi-regular if and only if, for any fuzzy subset $f$ of $S$ we have $f\preceq 1\circ f\circ 1\circ f$ (resp. $f\preceq f\circ 1\circ f\circ 1)$ and it is semisimple if and only if, for any fuzzy subset $f$ of $S$ we have $f\preceq 1\circ f\circ 1\circ f\circ 1$. The characterization of regular and intra-regular hypersemigroups in terms of fuzzy subsets are very useful for applications. 
Niovi Kehayopulu
math.GM