RDDOnto provides an ontological approach to the Rights Data Dictionary (RDD) part of MPEG-21one of the main Intellectual Property Rights (IPR) Management standardisation efforts. In order to build the ontology, the terms defined in the RDD specification have been modelled using OWL, trying to capture the greatest part of its semantics. The ontology allows formalising a great part of the standard and simplifying its verification, consistency checking and implementation. During the RDDOnto construction, some integrity problems were detected, which even have led to standard corrigenda. Additional checks were possible using Description Logic reasoning in order to test the standard consistency. Moreover, RDDOnto is now helping on how new terms can be added to the RDD and to integrate the RDD with other parts of MPEG-21 also mapped to OWL. Finally, there are the implementation facilities provided by the ontology. They have been used to develop MPEG-21 licenses searching, validation and checking. Existing ontology-enabled tools as semantic query engines or logic reasoners facilitate this.