well, at first thank you for your time a Ruta can have 0,n Puertos a Puerto can be part of 0,n Rutas the distance(which is also a attribute in Puerto and Ruta with other significant) indicates the distance beetwen the start of the Ruta and start of the Puerto. I need it to calculate a coeficient of the difficult of a Ruta. Thanks felix!! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4043020#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...