A new approach to interoperability between ODRL and MPEG-21 REL

A key issue for the real deployment of Digital Rights Management (DRM) systems is interoperability. A clear example is at the level of Rights Expression Languages (RELs), where two of them are a prominent role. On the one hand, ODRL (Open Digital Rights Language) is an initiative being used, for example, by the Open Mobile Alliance (OMA), a relevant industrial forum in the area of mobile and on the other hand systems MPEG-21 REL is an ISO/IEC standard. MPEG-21 REL is more complete, but rather complex although not exhaustive; this is why ODRL could be considered as a more flexible option. In this paper, we analyse two DRM specifications from OMA, and try to propose its implementation in an MPEG-21 environment. In addition tools able to work in both environments are presented. By defining an MPEG-21 REL DTD, a minor extension of the MPEG21 REL, and the use of the MPEG-21 IPMP (Intellectual Property Management and Protection), we are in fact specifying MPEG-21 REL profiles. This approach could simplify the implementation of MPEG21 REL applications and facilitate its interoperability with ODRL. In order to verify the feasibility of our proposal, we have implemented some tools that work with both MPEG-21 REL and OMA DRM.