Bill Presentment Architecture (BPA): Relation between Seeded data source/views Vs Custom Data source

 Hello All,

What is the Relation between Seeded BPA data source/views Vs Custom Data source/Views registered in BPA.

I'm planning to use let's say 40 attributes from seeded view and rest 10 from custom view. Iif there are various filter conditions applied in custom view, what's going to be the result if any of the filter condition applied doesn't allows invoice be picked up and the seeded view does?. Will the invoice be printed?

Is there a where clause relationship or UNION?

Ex: Select ----

         -----

      From Seeded_view

      where customer_trx_id=1000

       Select ----

         -----

      From Seeded_view

     where  'X'='Y'