On weakly connected domination in graphs

A dominating set D is a weakly connected dominating set of a connected graph G=(V,E) if (V,E@?(DxV)) is connected. The weakly connected domination number of G, denoted @c"w"c(G), is min{|S||S is a weakly connected dominating set of G}. We characterize graphs G for which @c(H)=@c"w"c(H) for every connected induced subgraph H of G, where @c is the domination number of a graph. We provide a constructive characterization of trees T for which @c(T)=@c"w"c(T). Lastly, we constructively characterize the trees T in which every vertex belongs to some weakly connected dominating set of cardinality @c"w"c(T).