| valid⊆(str, st0, st1), valid⊆(str, st, st0) ⊦ valid⊆(str, st, st1) |
⊦ valid⊆(str, st, st0) ↔ (∀ r, ty. validref(str, r, ty, st) → validref(str, r, ty, st0)) ∧ (∀ r. ¬ r ∈ st ∧ r ∈ st0 → ¬ junkref(str, r, st0))
(∀ r, ty. validref(str, r, ty, st0) → validref(str, r, ty, st1)) ∧ (∀ r. ¬ r ∈ st0 ∧ r ∈ st1 → ¬ junkref(str, r, st1)), valid⊆(str, st, st0) ⊦ valid⊆(str, st, st1)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st1, st0, str)]]