| validrefvalnotnull(str, st[rk], ty, st), rk ∈ st, st ⊆ st1 ⊦ validrefkeynotnull(str, rk, ty, st1) |
⊦ validrefkeynotnull(str, rk, ty, st) ↔ rk ∈ st ∧ validrefvalnotnull(str, st[rk], ty, st)
validrefvalnotnull(str, st[rk], ty, st), rk ∈ st, st ⊆ st1 ⊦ rk ∈ st1 ∧ validrefvalnotnull(str, st1[rk], ty, st1)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st1, ty, rk, str)]]