On the Jordan-Hölder decomposition of proof nets

Abstract.

Having defined a notion of homology for paired graphs, Métayer ([Ma]) proves a homological correctness criterion for proof nets, and states that for any proof net $G$ there exists a Jordan-Hölder decomposition of ${\mathsf H}_0(G)$. This decomposition is determined by a certain enumeration of the pairs in $G$. We correct his proof of this fact and show that there exists a 1-1 correspondence between these Jordan-Hölder decompositions of ${\mathsf H}_0(G)$ and the possible ‘construction-orders’ of the par-net underlying $G$.