Hi,
I was thinking of modifying the Ring Aromatic pharmacophore feature and realized that I don't understanding this feature definition at all.

The Ring Aromatic feature exists of 2 6-membered aromatic rings and 2 5-membered aromatic rings. Both 6-rings (or 5-rings, respectively) have exactly the same properties. Why is it necessary to include a fragment twice in the Ring Aromatic feature definition?
When I want to add a new fragment (ring) to this definition, do I have to include 2 copies of this ring?

Thanks in advance!