Abstract p-time proof nets for MALL: Conflict nets
  This paper presents proof nets for multiplicative-additive linear logic (MALL), called conflict nets. They are efficient, since both correctness and translation from a proof are p-time (polynomial time), and abstract, since they are invariant under transposing adjacent &-rules.   A conflict net on a sequent is concise: axiom links with a conflict relation. Conflict nets are a variant of (and were inspired by) combinatorial proofs introduced recently for classical logic: each can be viewed as a maximal map (homomorphism) of contractible coherence spaces (P_4-free graphs, or cographs), from axioms to sequent.   The paper presents new results for other proof nets: (1) correctness and cut elimination for slice nets (Hughes / van Glabbeek 2003) are p-time, and (2) the cut elimination proposed for monomial nets (Girard 1996) does not work. The subtleties which break monomial net cut elimination also apply to conflict nets: as with monomial nets, existence of a confluent cut elimination remains an open question. 
Dominic J. D. Hughes