I've previously blogged about NExpert Objects, you can find those postings here:
NExpert Object Videos
NExpert Review (MacTech)
Today a little birdie pointed me at a url that provides the complete set of Intelligent Rules Element manuals, IRE is the successor to NExpert Objects.
I've been reading through the manuals and have found it interesting, definitely not what I was expecting. IRE seems neither prolog or rete like, it provides fine grained control over the order of evaluation of field constraints. Looking forward to reading these more indepth over the coming weeks.