Dirichlet spaces on H-convex sets in Wiener space

We consider the $(1,2)$-Sobolev space $W^{1,2}(U)$ on subsets $U$ in an abstract Wiener space, which is regarded as a canonical Dirichlet space on $U$. We prove that $W^{1,2}(U)$ 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.Comment: 18 pages, 1 figure. Erratum has been added, which was accepted for publication in Bull. Sci. Mat