class real_arg_xcomp_canonical
{
    <: real_arg_xcomp;
    node(SArg).type=value(subst);
    node(SArg).top.sat = value(-);
    %%  desc.extraction = value(~adjx);
    $xcomp_by_adj = value(-);
    SArg +
        $arg.kind = value(scomp|prepscomp|prepvcomp|vcompcaus|acomp|vcomp|whcomp|vcompprog)
        ;
    SArg +
        $arg.kind = value(scomp|prepscomp|prepvcomp|vcompcaus|acomp|vcomp|vcompprog),
        node(SArg).top.extraction = value(-)
        |
        $arg.kind = value(whcomp)
        ;
}