An Architecture for the Interoperability between Rights Expression Languages Based on Xacml

None of the current initiatives to provide interoperability between Digital Rights Management (DRM) systems, such as CORAL [3] or Marlin [13], provide a global solution to enable different devices to render content governed by different DRM systems. Interoperability applies to different aspects of DRM, such as languages for rights expression, digital objects declaration and protection information declaration. We focus on the interoperability between Rights Expressions Languages (RELs). In this area, we have already done some work, including the definition of profiles for the MPEG-21 REL [14] standard. Based on those profiles for specific domains (such as the mobile or broadcasting ones), a couple of approaches have been developed for interoperability between licenses in different RELs, such as the use of extensible style sheets transformations or the use of high level modelling schemas. In order not to be restricted to specific profiles, this paper presents a solution based on the use of a XACML system based architecture to achieve interoperability between RELs. We demonstrate the feasibility of the proposed solution showing that the main elements of rights expressions can be expressed in XACML policies without loss of information. Furthermore, instead of translating between different RELs through an intermediate one, we directly map to XACML and perform the authorisation with it. In this way, we do not lose any information conveyed in the input REL.