SVD for explicit feedback and implicit feedback
explicit feedback, which includes explicit input by users regarding their interest in products. For example, Netflix collects star ratings for movies and TiVo users indicate their preferences for TV shows by hitting thumbs-up/down buttons.
implicit feedback, which indirectly reflect opinion through observing user behavior. Types of implicit feedback include purchase history, browsing history, search patterns,or even mouse movements.
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No negative feedback. By observing the users behavior, we can infer which items they probably like and thus chose to consume. However, it is hard to reliably infer which items a user did not like. This fundamental asymmetry does not exist in explicit feedback where users tell us both what they like and what they dislike.
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Implicit feedback is inherently noisy. While we passively track the users behavior, we can only guess their preferences and true motives. For example, we may view purchase behavior for an individual, but this does not necessarily indicate a positive view of the product. The item may have been purchased as a gift, or perhaps the user was disappointed with the product.
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The numerical value of explicit feedback indicates preference, whereas the numerical value of implicit feedback indicates confidence.