| is_fskey(sk) ⊦ addclass(class1, (sk × val0) ', st) = addclass(class1, (sk × val) ', st), sk .fs .class = class1 |
sk = fs ', is_fskey(sk) ⊦ addclass(class1, (sk × val0) ', st) = addclass(class1, (sk × val) ', st), fs .class = class1
[[CONCRETESIMPRULES : ([CSIMPELIM : ⊦ is_fskey(sk) → (fs = sk .fs ↔ sk = fs ')])], [EXTRATERMS : (sk, fs)]]