| validval(str, rk, val, st), rk0 × val0 ∈ rkvs, validval(str, rk0, val0, st) ⊦ validval(str, rk0, val0, st[rk, val]) |
⊦ validval(str, rk, val, st) ∧ validval(str, rk0, val0, st) → validval(str, rk0, val0, st[rk, val])
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (val, rk, st, val0, rk0, str)]]