Introduction to Logic Programming with Clojure - Ambrose Bonnaire-Sergeant 

It's science. It takes time, motivation & energy to learn it. Besides, look at the number of views. ~5000 by now. For practical purposes it means there's no one around who understands this and whom you could hire for your project.

It is. Erlang is based on Prolog, a classic logic programming language.

Joe Armstrong wrote the first Erlang compiler in Prolog, and Erlang's syntax is derived from that of Prolog, but Erlang is not a logical programming language. Its focus is functional programming & concurrency.

I know a case in Sweden where I believe prolog or similar was used to ensure that the train scheduling system did not allow unsafe train configurations (collisions, or two trains in same signal block).

@@paxinum Indeed, where it would be able to be used is determined by the domain. Almost all programming jobs you can get are built on top of logic to such a higher abstraction that the average dev at most just uses an (if) statement. There isn't any industry presence for doing beautiful clear-thinking because the domains don't necessitate it in the short term, and good luck finding an employer-let alone a manager-who ever thinks beyond the short term. Mostly you are too busy learning a framework of the month and shipping some buggy mess which works just well enough. There's barely *any* presence of LISP. C and his garbage bastard children have eaten the world; we are all more impoverished as a result.