Yeah, I agree. I've also used CLIPS on several projects. Also Prolog. These aren't easy systems for a non-programmer to use directly.

You can make CLIPS (or, IMO any rule-based system) easy to use like this in one dimension, but not the dimension you want. For example, I had a system for diagnosis according to DSM-IV criteria. It had a nice interface for users to enter new "facts", which the rules would then run against. But, allowing users to be able to add new rules (and preserve the existing dependencies and logic) would have been way more difficult (or impossible).

How about the "standard" way of solving this? From your description of the problem, it's exactly what OO programming is about. You create business objects in clean OO code, and give them methods that model the business rules. The methods only allow the various operations to go through if whatever criteria is met. This is a really clean way to code, and yeah - you need an OO programmer to maintain it. But, the problem itself requires it, I think.