+ # we do not normally return the "other" partners referenced by an relation,
+ # e.g. if we return a way A that is referenced by relation X, and there's
+ # another way B also referenced, that is not returned. But we do make
+ # an exception for cases where an relation references another *relation*;
+ # in that case we return that as well (but we don't go recursive here)
+ relations += relations.collect { |relation| relation.containing_relations.visible }.flatten
+
+ # this "uniq" may be slightly inefficient; it may be better to first collect and output
+ # all node-related relations, then find the *not yet covered* way-related ones etc.
+ relations.uniq.each do |relation|
+ doc.root << relation.to_xml_node(user_display_name_cache)
+ end