A star-dominating set is a subset "D" of "V" such that, for every vertex v in "V", the star of "v" (the set of edges adjacent to "v") intersects the star of some vertex in "D". Clearly, if G has isolated vertices then it has no star-dominating sets (since the star of isolated vertices is empty). If G has no isolated vertices, then every dominating set is a star-dominating set and vice-versa. The distinction between star-domination and usual domination is more substantial when their fractional variants are considered.