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