In my country Expert System class is mandatory class if you want to take AI specialization in most universities. In class I learned how to make a rule base system, forward chaining, backward chaining, [Prolog][1], etc. I enjoyed the class until I read a few comments in Stackoverflow that Expert System is no longer included in the AI field, some top university have stopped teaching that again. I found the old screenshot one of the comments: [![enter image description here][2]][2] Is that true? why? And from industrial view, with the rise of machine learning, is the expert system still in use today? [1]: https://id.wikipedia.org/wiki/Prolog [2]: https://i.sstatic.net/EdsVc.jpg