Section BiComposition.
Variables X Y Z: Type.
Variable TX: reduction_t A X.
Variable TY: reduction_t A Y.
Variable TZ: reduction_t A Z.
Variable R: relation2 X Y.
Variable S: relation2 Y Z.

Lemma wexpansion_comp: wexpansion TX TY R -> wexpansion TY TZ S -> wexpansion TX TZ (comp R S).