OBIEE 11g.

I have been experimenting with parent-child hierarchies, and have encountered something interesting.

We have a parent-child hierarchy set up that shows Sponsor relationships. So for example

Agency A is a federal agency, which is at the top of the hierarchy.

Agency B, is a state agency, and a child of Agency A

Agency C is a county agency, and a child of Agency B

Agency D is a local agency, and is a child of Agency C.

Client E, is an actual client of Agency D, and is the fact level.

Agency A

   |___Agency B

       |___Agency C

           |___Agency D

               |___Client E

Here is my situation: If I filter Agency B for "Pennsylvania", I get the following message:

The layout of this view combined with the data, selections, drills, or prompt values chosen resulted in no data. Undo drills and view prompt values.

However, if I view the entire list of states, then select Pennsylvania, right click, and select "Keep Only",

then only Pennsylvania is displayed, and I can now drill down through county agencies, and then local agencies, without any issues.

So my question are:

1. What is the difference between doing a filter, and doing the Keep Only?

2. For anyone that uses a parent-child hierarchy, how do you allow users to initially select the value

of a specific level (eg: specifically selecting Pennsylvania) instead of viewing the entire list of all 50 states.

Thanks in advance fro any help anyone can offer.