On Characterization of Open Sets in Euclidean Spaces

A ternary semigroup is a nonempty set T together with a ternary oper- ation [abc] satisfying the associative law [[abc] de] = [a [bcd] e] = [ab [cde]] for all a, b, c, d, e ε T. A map f between topological spaces X and Y is called open if the image of each set open in X is open in Y. The pur- pose of this paper is to give an abstract characterization of the ternary semigroups of open maps defined on open sets in Euclidean n-spaces.