Many people have thought about it, but I haven't heard of any solid implementations other than possibly the RoR client-side validation plugin mentioned by roryo

Many people have thought about it, but I haven't heard of any solid implementations other than possibly the RoR client-side validation plugin mentioned by roryokane [http://news.ycombinator.com/item?id=635997 http://news.ycombinator.com/item?id=635997]. A recent article in CACM describes a promising approach with less promising syntax: http://portal.acm.org/citation.cfm?doid=1461928.1461949 http://portal.acm.org/citation.cfm?doid=1461928.1461949