| is_fskey(sk), ∀ str, r, ty, class, st. validref(str, r, ty, addclass(class, fis0, st)) ↔ validref(str, r, ty, st) ⊦ sk .fs .class = class, validref(str, r, ty, addclass(class, fis0, st)) ↔ validref(str, r, ty, st) |
sk = fs ', is_fskey(sk), ∀ str, r, ty, class, st. validref(str, r, ty, addclass(class, fis0, st)) ↔ validref(str, r, ty, st) ⊦ fs .class = class, validref(str, r, ty, addclass(class, fis0, st)) ↔ validref(str, r, ty, st)
[[CONCRETESIMPRULES : ([CSIMPELIM : ⊦ is_fskey(sk) → (fs = sk .fs ↔ sk = fs ')])], [EXTRATERMS : (sk, fs)]]