Ah thanks for clarifying. Now it makes sense.
Are there any real world applications for this, for us mortal web developers?
If you're asking "is there anything in the wild that I would know of and uses this?" then the answer is probably "no".
Most of the prolog projects I've ever seen are pretty inbred; implementing compilers or interpreters, hooks for another language-type things. Though it must be said that I'm not deeply embedded in the prolog community.