I hope this is not that much of easy to design a DBD (thats also using Logical relationship). Just to design a small DBD with 4 levels will take a long time, and it is DBAs work.
If you want know the concept, you can refer in any IMS manual, what are differences you get in DBD(like LCHILD) and in PSB when compared to narmal database. Hope you can create a DBD with Logical relationship if you have prior expereince in creating DBDGENs.
I cannt help in this situation.Anyone can explain him to create a DBD with Logical relationship.