Dirichlet spaces on H-convex sets in Wiener space

We consider the (1,2)-Sobolev space W1,2(U) on subsets U in an abstract Wiener space, which is regarded as a canonical Dirichlet space on U. We prove that W1,2(U) has smooth cylindrical functions as a dense subset if U is H-convex and H-open. For the proof, the relations between H-notions and quasi-notions are also studied.