The BMM is a perfect star schema, so you can't really join 2 dimensions like a snowflake...
You can join them inside the LTS of your logical dimension and then create 2 different tables in the presentation layer to still display them as separate objects, or maybe one of your 2 dims is supposed to be a fact?
Review and rethink your model to define if you really need to join the 2 dimension keeping in mind you must have a perfect star in BMM to define the best model for your need.
You can create a report with two dimension tables, Oracle Business Intelligence Solutions: OBIEE 11g : Implicit Fact Column
However it depends on your fact table, OBIEE by default get the least time consuming path, but you can set an implicit fact column to force the the path of the OBIEE.
Hope this help!
I have an implicit fact defined in the RPD (OBIEE 18.104.22.168) and it works fine as long as i am using dimension only attributes without any aggregate function.
Eg. Dim1.xxx, Dim2.yyy
But the moment i apply an aggregate function, say max(Dim1.xxx), Dim2.yyy -> implicit fact gets ignored by the physical query generated by obiee. It uses another fact instead and brings in result different than expected.
Any suggestions why this could have been happening?