| ⊦ (fnode(fid) = tree → (∃ fids. ∀ fid0. fid0 ∈ fids ↔ fid0 = fid)) ∧ ((∀ str. str ∈ sdt → (∃ fids. ∀ fid. fid ∈ fids ↔ fid ∈ sdt[str].fids)) → dnode(md, sdt) = tree0 → (∃ fids. ∀ fid0. fid0 ∈ fids ↔ fid0 ∈ sdt.fids)) |
fnode(fid) = tree ⊦ ∃ fids. ∀ fid0. fid0 ∈ fids ↔ fid0 = fid
dnode(md, sdt) = tree0, ∀ str. str ∈ sdt → (∃ fids. ∀ fid. fid ∈ fids ↔ fid ∈ sdt[str].fids) ⊦ ∃ fids. ∀ fid0. fid0 ∈ fids ↔ fid0 ∈ sdt.fids