| validrefkeynotnull(str, rk, ty1, st) ⊦ validrefnotnull(str, st[rk] .refval, ty1, st) |
⊦ validrefkeynotnull(str, rk, ty, st) ↔ rk ∈ st ∧ validrefvalnotnull(str, st[rk], ty, st)
rk ∈ st ∧ validrefvalnotnull(str, st[rk], ty1, st) ⊦ validrefnotnull(str, st[rk] .refval, ty1, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, ty1, rk, str)]]