“…RÔH 1 , r 1 ÕÔH 2 , r 2 ÕÔH, r future Õ; (3) there exists at least one activation frame: fs f :: fs ½ and environment env cur , arguments args cur and post-condition Q cur ; such that (4) safeFrame Ôf, H 1 , r 1 , env cur , args cur , Q cur Õ; and (5) safeStack Ôfs, H 2 , r 2 , env cur , args cur , Q cur , env , args, QÕ.…”