Here are my understanding about Legacy connectivity rules:
1. If the legacy system is CORBA based use RMI-IIOP to connect to the system. 2 2. If the legacy system is Terminal based, use Screen Scrappers, (wrap in EJB or applet) 3. If the legact system is Messaging Queue Series based, use JMS system to connect to. 4. If the legacy system is ODBC based, use JDBC-ODBC bridge. 5. If the legacy system provides only native libararies, wrap the library in JNI.
Please give some more thumb rules like this, if any body knowing.