Big fan of CLIPS! Rule based expert systems are so ubiquitous in business and scientific codes, yet a lot of devs are not even familiar with pattern matching let alone powerful rules engines like CLIPS.
This has been similar to my experience. Rules Engines like CLIPS are just outside of the bounds of "cheap enough to spend time learning on the off-chance it is indeed better than what we've already written."
I'll admit, even as a programmer who's tried a lot of languages, I know a lot more about logic program and unification-based languages – and nothing practical about expert systems and their core algorithms.
