I once worked for a company where we used it to parse source code (COBOL in this case -- a BIG market full of unmaintainable code), let people restructure it gr

I once worked for a company where we used it to parse source code (COBOL in this case -- a BIG market full of unmaintainable code), let people restructure it graphically, and then the system would regenerate new source code. The generation of solutions from a database of facts is one area where Prolog really shines and that's what I love most about it. It's definitely a "here's a bunch of data, here's my starting point, over there is my desired ending point, now get me from here to there and I don't care how you do it as long as it's valid" programming language. Plus, I love that a Prolog application is, in many respects, nothing more than a side effect of a proof being generated. I also once used it in a startup for an system that could dynamically generate complex application user interfaces depending on individual users' profiles and preferences, but we ended-up scrapping that feature.