Hi, I was wondering what your opinions are on the necessity of negative conditions in production rules? The reason I am interested is that I am currently developing a Java embedding of a rule-based programming language myself, with similar expressive power as the current Drools language (i.e.: forward chaining rules without negative conditions). I am pleased to see a system as Drools became this popular and widely used and accepted without support for negative conditions. It strengthens my feeling that a language could do without (and without the complexities of implementing it efficiently...).
So, the main question for the discussion I am hoping to get started here (probably you've had it before somewhere, in which case a summary of the outcomes would be much appreciated): are negative conditions necessary? Are they missed in practice a lot? Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
