1. A method for providing a recommendation to a user, comprising: receiving context information associated with the user; updating a plurality of user models based on the received context information; identifying a spatial data structure that stores a plurality of items, wherein the spatial data structure corresponds to a vector space, and wherein a respective item is stored within the spatial data structure based on a vector value associated with the item; querying the spatial data structure to obtain a first set of recommendable items that have vector values within a predetermined range; calculating a score for each item within the set of recommendable items based on the plurality of the user models and a characterization vector associated with each item; ranking the items within the set of recommendable items based on calculated scores; and recommending one or more top-ranked items to the user.