class modifier_on_coo
{
    + s_adj_pos;
    node(Root).cat = value(coo);
    Foot < Incise;
    %% restriction: no more than one modifieur per coo node
    %% node(Foot).top.modifier = value(-);
    %% node(Root).bot.modifier = value(+);
  desc.dependency = value('mod');
}