MAYBE
We consider the system theBenchmark.

  Alphabet:

    const : [a * b] --> a 
    fix : [(f -> g) -> f -> g] --> f -> g 
    subst : [c -> d -> e * c -> d * c] --> e 

  Rules:

    const(x, y) => x 
    subst(f, g, x) => f x (g x) 
    fix(f) x => f fix(f) x 

This AFS is converted to an AFSM simply by replacing all free variables by meta-variables (with arity 0).