Even aside from changing the syntax, you often have to do this to modify the resolution strategy, such as using breadth-first instead of depth-first search, or

Even aside from changing the syntax, you often have to do this to modify the resolution strategy, such as using breadth-first instead of depth-first search, or add probabilistic or fuzzy logic. A lot of papers on Prolog from the 80s start with "what would it be like to use logic-X from Prolog?" You can do a lot of interesting deep cuts like this without a huge amount of work. Prolog even has a built-in context-free parser that works the same way: definite clause grammars.