“The one-to-five-star paradigm is not going to accurately assess their customers’ attitudes toward movies. The similarity space is more like Dr Hinton’s reference to a ten-dimensional library where neighbourhood relationships don’t just go along a Dewey Decimal line but also style, mood, season, director, actors, cinematography, and yes the “People like you” metric (“collaborative filtering”, a spangled bit of jargon). For them the preferences evolve fairly quickly over time. That has to make it hard. If your users’ preferences evolve over time: good luck, it may be quite hard.” - × × ×