Construction of association schemes from difference sets

Let H and F be two finite groups. In group theory it is known that an extension G of H by F is characterized by the action of F on H and a factor set associated with the action, and the two-dimensional cohomology group with respect to the action is defined when H is Abelian. In this paper we consider an analogy of the above for association schemes and construct such extensions of association schemes from a difference set when H is an elementary Abelian group.