| (st[rkvs][_mode]) ≠ noval, st[_mode] = noval ⊦ validmode(str, st[rkvs]) ↔ _mode ∈ st, _mode ∈ rkvs |
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ ∅[rk] = noval], [CSIMPSEQ : ⊦ ¬ rk ∈ st → st[rk] = ∅[rk]], [CSIMPSEQ : ⊦ ¬ rk ∈ rkvs → (st[rkvs][rk]) = st[rk]])]]