The growth of available personalization services and the heterogeneity in content and representation of therein exploited User Models (UMs), raise a need for a mechanism allowing to aggregate partial UMs generated by other services. Such a mechanism will allow reuse of partial UMs in multiple personalization services that may need it. This paper discusses the details of a decentralized mediator for cross-domain and cross-technique translation and aggregation of partial UMs. The mediator facilitates enriching UMs managed by personalization services and improving the quality of the provided personalization.