how bout amazon's recommendation systems? or ad placements? or google search? google what did you mean? ocr? algorithmic trading? what field are they in if not

how bout amazon's recommendation systems? or ad placements? or google search? google what did you mean? ocr? algorithmic trading? what field are they in if not AI? sure, the techniques are heterogeneous and there seems to be no one unifying theory but the field is a bit like that.