Mathematica by nature acts like Lisp. a variety of Lisp languages are free (ie, via Ubuntu which is a module for Windows 10 you can check out). Lisp was in older journals as a language conducive to artificial intelligence programming.
Lisp would only restrict what you are used to being able to do with lists and expressions. Studying an introduction to lisp book would enlighten you as to a style of node traversal programming, though.
(problems with lisp: few use it, it has a high learning curve. few drivers - meaning it will be limited to text output - no graphics. the versions that are "very reliable" and standardized are non-free, the free versions change standards so that older programs / examples will crash)
Mathematica 11.3 has an immense wealth of DAG, some which likely were (began) by Roman Maeder.
Mathematica 11.3 has extended logic solving (symbols, functions, tutorials).
The old articles are interesting but no longer needed if your running any recent version of Mathematic. It was written back for Version 2.2. First version i owned was 4.0 in the (latter 90's) :)
Prolog is also something Mathematica does you won't need.