[rules-users] [newbie] Using rules to enforce constraints?

Hi, Apologies if this has been covered somewhere, couldn't find it in the archives. I'm wondering about ability / sensibility of above. For example, say I want to model the following rules: 1. A customer must be suspended if they default on a payment 2. A suspended customer may place any orders Now the first one I can readily map to the when/then format of production rules. But I can't see how to elegantly represent the second one - at least not in a transactionally clean manner. I could write: when c: Customer (status == "suspended") o: Order ( customer == c) then o.reject() #etc. But that's not really what I want to achieve. Rather, I'd like the check enforced before the order was created, not after. Or maybe I'm just thinking wrong? Main influence is RDBMS, where I'd write a trigger that would stop the transaction completing if violated. Hope that makes sense, and thanks in advance. - Scoot.