⊦ as = as0 ↔ (∀ adr. adr ∈ as ↔ adr ∈ as0)
⊦ (∀ adr. adr ∈ as0 \ as1 ↔ adr ∈ ∅) ↔ as0 ⊆ as1
Used terms: ∅, as0 \ as1