16. An apparatus of claim 10 , wherein the apparatus is further caused to: generate and/or retrieve one or more item models associated with the one or more abstraction levels; and select at least one of the one or more item models for generating the one or more recommendations based, at least in part, on the one or more privacy policies, the one or more security policies, the selected at least one user model, the requested abstraction level, or a combination thereof.
10. An apparatus comprising: at least one processor; and at least one memory including computer program code for one or more programs, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following, determine an ontology for specifying a hierarchy of one or more abstraction levels for items data used in latent factorization models; generate one or more user models for the items data corresponding to each abstraction level of the ontology; process at least one request for one or more recommendations (a) to determine a requested abstraction level, and (b) to determine a privacy level, a security level, or a combination thereof associated with the at least one request; process the privacy level, the security level, or the combination thereof against one or more privacy policies, one or more security policies, or a combination thereof to determine permission to access the requested abstraction level; generate and/or retrieve the at least one of the one or more user models based, at least in part, on whether the at least one of the one or more user models exists at the requested abstraction level, select at least one of the one or more user models for generating the one or more recommendations for one or more applications, one or more services, or a combination thereof based, at least in part, on the one or more privacy policies, the one or more security policies, or the combination thereof; and wherein the one or more abstraction levels correspond to different levels of the privacy policies and the security policies of the one or more user models.