| abs-keys(orphans(fs0, ri0)) = abs-keys(orphans(fs, ri)) ⊦ orphans(fs0, ri0) = orphans(fs, ri) |
⊦ ks = ks0 ↔ (∀ key. key ∈ ks ↔ key ∈ ks0)
abs-keys(orphans(fs0, ri0)) = abs-keys(orphans(fs, ri)) ⊦ ∀ key. key ∈ orphans(fs0, ri0) ↔ key ∈ orphans(fs, ri)
Used terms: orphans(fs, ri), orphans(fs0, ri0)