Whether definitive legal opening could be granted for future maintenance installments not yet due when the enforcement began.
No; arrest under Art. 271 SchKG may accelerate an existing claim, but it does not make future maintenance installments due for purposes of legal opening if they were not yet due when the debt collection started.
Future maintenance claims arise continuously and are not part of an already existing debt; the arrest creates no independent maturity beyond the arrest context. Since the payment order was served before the younger sons' future installments became due, definitive legal opening for that part was unlawful.