@hennevogel I agree the attributes are unnecessary here; but @gopesht's goal was to create Objects for sponsorship that were in line with the existing app's structures.  To that end, having

* Conference has many Sponsorship Registrations,
* Organization belongs to a SponsorShip Registration

would be the minimum that meets the requirements *and* conforms to the project's object model.  Adding

* Conference has many Sponsorship Levels
* Sponsorship Registration belongs to a Sponsorship Level

while not required, definitely conforms to the project, and supports the feature at hand.

I'll work with @gopesht to control the scope & feature creep.