Section PlusWf.
Variable X: Set.
Variable S: relation X.
Variable TX: relation X.
Hypothesis HS: diagram TX S (star TX) (plus S).
Hypothesis Hwf: well_founded (trans S).
Let Hpwf: well_founded (trans (plus S)) := plus_wf Hwf.
Variable TX': relation X.
Hypothesis HS': diagram TX' S (comp (star TX) TX') (plus S).

(** Lemma 4.3 *)
Lemma diagram_plus_wf_1: strong_commute (comp (star TX) TX') (plus S).