Contract - How to model

Hi,

I am thinking about options to model a contract for an energy company (electricity and gas supply).
A contract has start and an end date (typically end date is blank or filled in with 9999 if the contract is active).
The 'product', customer,premise,installation etc are then attached

Now would this be typically modelled as a fact (likely fact-less fact table)?
How would changes to the contract typically modelled eg: if the customer changed the contract rate they were on.
Would the contract be a dimension as well as a fact for changes?

The closest example I could find was the insurance example in the "data warehouse toolkit".
(but didn't quite give me what I needed).

Any help or advice would be greatly appreciated.

I think an applicable example that Kimball has written about is product price. The attribute could live in a dimension or fact. In your case, I would put rate in the fact table.