| validrefkeynotnull(str, rk, ty, st) ⊦ validrefkeynotnull(str, rk, ty, st0 ∪ st) |
⊦ validrefkeynotnull(str, rk, ty, st) ↔ rk ∈ st ∧ validrefvalnotnull(str, st[rk], ty, st)
rk ∈ st ∧ validrefvalnotnull(str, st[rk], ty, st) ⊦ validrefkeynotnull(str, rk, ty, st0 ∪ st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, ty, rk, str)]]