1. A method of feature vector indexing, comprising the steps of: providing a plurality of feature vectors, each feature vector indicative of one of a plurality of objects, wherein each feature vector comprises at least one primitive, each primitive being associated with an attribute of the object and identifying a plurality of features, each feature having an associated feature coefficient; using a distance metric to select index values which are indicative of features of the feature vector; providing a target feature vector and a plurality of user weights; generating a constraint based on the target feature vector and the plurality of user weights; and applying the constraint to the index values so as to select a subset of the feature vectors.