| key ∈ ks ⊦ # ks = 0, ks = ∅, (ri ⊖ key) ⊖ ks = ri ⊖ ks |
⊦ ri = ri0 ↔ (∀ key. (key ∈ ri ↔ key ∈ ri0) ∧ (key ∈ ri → ri[key] = ri0[key]))
key ∈ ks ⊦ # ks = 0, ks = ∅, ∀ key0. (key0 ∈ (ri ⊖ key) ⊖ ks ↔ key0 ∈ ri ⊖ ks) ∧ (key0 ∈ (ri ⊖ key) ⊖ ks → ((ri ⊖ key) ⊖ ks)[key0] = (ri ⊖ ks)[key0])
Used terms: ri ⊖ ks, (ri ⊖ key) ⊖ ks