| is_valid_ref(str, r, st), level⊆(str, str0) ⊦ is_valid_ref(str0, r, st) |
⊦ is_valid_ref(str, r, st) ↔ is_obj(str, r, st) ∨ is_array(str, r, st)
is_valid_ref(str, r, st), level⊆(str, str0) ⊦ is_obj(str0, r, st) ∨ is_array(str0, r, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, r, str0)]]