Part - "References Document"

Hi all,

It was a surprise to note that only Documents under the Type "Reference Document" can be used in the Part to Doc relation called as "References Document".

Why is this?

I cant find any possibility with change this behavior using the Relationship Constraints.

This means that when we design the document data model long before we start using Parts, we should decide whether it is going to be a "Reference document" or not?

Sounds strange! or is there any way out?

Basically, we want to be flexible in the way a document can be used --- as "Described by" document or as "References Document".

Best Regards

Hari