Business Rule Instance

Hi all..

I read on ebook that said :

one rule instance is shared across all instances of business type.

I want to know a foundation / reason to said that ?

this is my current understanding, I hope Rocky or someone else could explain to me  to update my understanding :

we insert code to add a rule in

protected override void AddBusinessRules()

{

BusinessRules.AddRule(new MyRule( ..... ));

}

and then when each my business type instances is created this method is called, Is it not mean that I add a new MyRule for each my business instance ?

thanks a lot

stefanus