I once asked my Prolog instructor why this all takes so long. His reply: "How well are you prepared for the next ISO meeting?" At that point, I realized that i

I once asked my Prolog instructor why this all takes so long. His reply: "How well are you prepared for the next ISO meeting?" At that point, I realized that if you prepare yourself in earnest for, say, the standardization process, or even to accomplish any concrete improvement in Prolog systems (such as better indexing, more advanced constraints, faster garbage collection etc.), then there is so much to do that there is barely enough time to do it properly! Hence, I think it is fair to say we are are progressing as fast as we can, and such complex projects as building a full-fledged Prolog system inherently take an amount of time that we are not yet fully accustomed to. Prolog systems have been in development for many decades and are still being improved all the time. In my view, they are only now becoming truly interesting, with many great features such as multiple argument indexing, tabling and expressive constraints.