First, Sorry for the Route/Road mismatch! In fact is it Road, i checked it before. The structure: Location ___|_______Road ___________ |____________________ IATA PK -----------> ORIGIN PK +FK spacee -----------> DESTINATION PK + FK So IATA is a String of an Location/Place and Road has a StartPoint (ORIGIN) and an EndPoint (DESTINATION). So Road has a double relation with Location. The idea behind this structure, in Java, is to know from one Road, for example, which the Details of the Origin/Destination from type Location are without using SQL and just work with Java classes. Best regards D6L View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4227478#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...