static Collection<WebRelation> web_relationObjects(Web web) {
  ifdef WebWithRelationsMap
  if (web.relations != null)
    ret values(web.relations);
  endifdef
  new L<WebRelation> l;
  for (WebNode n : web.nodes)
    if (n instanceof WebRelation)
      l.add(n/WebRelation);
  ret l;
}