The humans (oracles) building the model.
'In an extension of Gödel’s incompleteness theorem—where the axioms of a system cannot be proved within that system—Turing showed the limits of computation: All computers are dependent on outside programmers that he called “oracles.” He wrote, “We shall not go any further into the nature of this oracle apart from saying that it cannot be a machine.”'
George, Gilder. Gaming AI: Why AI Can't Think but Can Transform Jobs (p. 21)