Ask HN: What are some interesting examples of Prolog?

I'm trying to source some programs and libraries written in Prolog to gain a better understanding of how a complete application is put together. Lots of Hello, World-esque examples out there, but looking for things that are a little less trivial.

I did come across terminusdb: https://github.com/terminusdb/terminusdb which looks interesting.

Any other codebases people would recommend that are worth a read?