| as2 \ as1 = as3, as1 \ as0 = as4, as1 ⊆ as2, as0 ⊆ as1 ⊦ as2 \ as0 = as3 ∪ as4 |
as0 ⊆ as1, as1 ⊆ as2, as0 ⊆ as2 ⊦ as2 \ as0 = (as2 \ as1) ∪ (as1 \ as0)
Used simplifier rules: sub-trans: ⊦ as ⊆ as0 ∧ as0 ⊆ as1 → as ⊆ as1; (forward) from specification set-basic[node-store]