I think he meant ML as the family of meta programming languages?
He did say systems though so you are probably right
He did say systems though so you are probably right
Btw, Prolog and ML might look like distant cousins: e.g. you use recursion and pattern matching in both. But under the hood there are big differences that arise from Prolog's logic programming paradigm: for instance, you can use append(L1, L2, L3) both to concatenate and split a list, depending on the variables you set:
append([1,2], [3,4], X) % ==> X=[1,2,3,4]
append([1,2], Y, [1,2,3,4]) % ==> Y=[3,4]