| bfwsim(IOAut(cstart, cstep, cext), IOAut(astart, astep, aext), r) ⊦ nfwsim (IOAut(cstart, cstep, cext), IOAut(astart, astep, aext), r, λ cs, ca, cs', as. min (λ n. ∃ asl, aal, aa, as1. frag*(IOAut(astart, astep, aext))(asl, aal) ∧ aext !(aal) = [] ∧ asl.head = as ∧ (∀ as. as ∈ asl → r(as, cs)) ∧ cext(ca) = aext(aa) ∧ n = # aal ∧ astep(asl.last, aa, as1) ∧ r(as1, cs'))) |