anchor.diff:      {ProductElemDataStore, ProductEventDataStore} =
           orddict:fold(
             fun(ElemL, ProvenanceL, AccProductDataStore0) ->
  -                  case subtract_removed(ProvenanceL, ValidEventsL1) of
  +                  case state_oorset_ps:subtract_removed(ProvenanceL, ValidEventsL1) of
                         [] ->
                             AccProductDataStore0;
                         RestProvenanceL ->
                             orddict:fold(
                               fun(ElemR, ProvenanceR, AccProductDataStore1) ->
  -                                    case subtract_removed(ProvenanceR,
  -                                                          ValidEventsR1) of
  +                                    case state_oorset_ps:subtract_removed(
  +                                           ProvenanceR, ValidEventsR1) of
                                           [] ->
                                               AccProductDataStore1;
                                           RestProvenanceR ->
                                               ProductElem = {ElemL, ElemR},
                                               ProductProvenance =
  -                                                cross_provenance(
  +                                                state_oorset_ps:cross_provenance(
                                                     RestProvenanceL, RestProvenanceR),
                                               ordsets:fold(
                                                 fun(Dot, AccProductDataStore2) ->
  
positive.code:                                                     IntersectElem =
                                                          get_inter_elem(ElemL, ElemR),
                                                      IntersectProvenance =
                                                          cross_provenance(
                                                            RestProvenanceL,
                                                            RestProvenanceR),
                                                      ordsets:fold(
  
negative.code:     lists:foldl(FolderFun, new(), V).
  
  %% @private
  join_all_events({vclock, AllEventsA}, {vclock, AllEventsB}) ->
      {JoinedAllEvents, RestB} =
          lists:foldl(
  