| ⊦ key0 ∈ (ri ⊖ ro) \ datakeys(key, n, ri) ↔ key0 ∈ (ri \ datakeys(key, n, ri)) ⊖ ro, key ∈ ro |
⊦ key ∈ ri \ ks ↔ key ∈ ri ∧ ¬ key ∈ ks
⊦ key0 ∈ ri ⊖ ro ∧ ¬ key0 ∈ datakeys(key, n, ri) ↔ key0 ∈ (ri \ datakeys(key, n, ri)) ⊖ ro, key ∈ ro
Used terms: datakeys(key, n, ri), ri ⊖ ro, key0