Just to consider a possible alternative for grouping elements like PortGroup, LinkGroup (and maybe others). Just I'm thinking. <port id="p1"> ... </port> <port id="p2"> ... </port> <port id="p3"> ... </port> <collection:set id ="c1"> <port idRef="p1"/> <port idRef="p2"/> <port idRef="p3"/> </collection:set> <port idRef="c1"/> <- higher level port <collection:set id ="c2"> <port idRef="p1"/> <port idRef="p2"/> <port idRef="p3"/> </collection:set> <node idRef="c2"/>) Roman