MPEG-21 Rights Expression Language: Enabling Interoperable Digital Rights Management

he Internet has spawned a revolution in the way people distribute content and access services. At the same time, the availability of broadband and wireless networks has increased, as have the capability and portability of computing and consumer electronic devices. These factors have fueled the development of new technologies to automate, manage, and secure content flow and service access over the Inter-net. The recently approved ISO standard, MPEG-21 Rights Expression Language (REL), is one such technology. 1 This language is precise, flexible , extensible, and rich in expressing rights. Thus, it can support reliable, flexible, and cost-effective interoperable digital rights management (DRM) systems and applications for electronic commerce and enterprise management of content and services. (See the " Benefits of Having an REL in Digital Rights Management " sidebar for the importance of an REL for DRM systems.) Objectives The MPEG-21 REL is an XML-based rights expression language for specifying terms and conditions regarding the authorized distribution and use of any content, resource, or service. Its goals are to ❚ define a machine-interpretable language's syntax and semantics to specify rights unam-biguously; ❚ provide an authorization model to determine if a principal has the right to act on a resource according to REL expressions; and ❚ support many business models in the end-to-end distribution value chain. The MPEG-21 REL provides flexible, interoper-able mechanisms to support transparent, augmented use of digital resources in publishing, distributing, and consuming digital content while protecting such content and honoring the rights, conditions, and fees specified for that content. The MPEG-21 REL also specifies access and use controls for digital content when financial exchange isn't part of the terms of use, and it supports the exchange of sensitive or private digital content. This language isn't just for the entertainment industry. Enterprises and individuals can use it to enable the authorized distribution and persistent protection of valuable data, content, and resources in accordance with privacy and confidentiality requirements. The MPEG-21 REL must also be rich enough to express a wide variety of business models and to enable multitier distribution and use of all types of digital content. The MPEG-21 REL's primary function is to specify rights regarding digital resources. Using this language, anyone owning or distributing digital resources can identify which principals (users, groups, devices, systems, and so on) may use those resources, the rights available to those principals, and the terms and conditions regarding the allowable exercise …