Why doesn't Oracle have foreign keys in Oracle Apps/ E-Business Suite?
I observed that Oracle doesn't have/use referential constraints on the Oracle Apps 11i Schema. All the logic is contained in PL/SQL packages.
This seems odd coming from a RDBMS major.
I believe the main reason for not using strong referential constraints is that this suite has to deal with legacy data during setup. Most of the time you will import historical data in the ERP and this data may be incomplete.
I don't think you should view the e-business design as a reference model since it is voluntarily left incomplete (so that you can custom it to your needs).