Introducing OMA – Open Mobile Alliance
The Open Mobile Alliance – formerly known as the WAP Forum – was formed in June 2002 by nearly 200 companies including the world‚s leading mobile operators, device and network suppliers, information technology companies and content and service providers. Goals of OMA are among others to deliver high quality, open technical specifications based upon market requirements, and to be the catalyst for the consolidation of standards activities within the mobile data service industry. OMA cooperates with other existing standards organizations and industry fora. Its focus is on the development of mobile service enabler specifications, which support the creation of market driven, interoperable end-to-end mobile services. Enablers are collections of specifications (enabler releases), which together form something like a standard for a service area fulfilling a number of related market requirements, e.g. a download enabler, a browsing enabler, a messaging enabler, a location enabler, etc.

Open Digital Rights Language Initiative
The Open Digital Rights Language Initiative is an international effort aimed at developing an open standard for rights expression in the DRM sector and promoting the Open Digital Rights Language (ODRL) within standards bodies. The ODRL specification supports an extensible language and vocabulary (data dictionary) for the expression of terms and conditions for any content including permissions, conditions, constraints, requirements, and offers and agreements with rights holders. ODRL is intended to provide flexible and interoperable mechanisms to support transparent and innovative use of digital resources in publishing, distributing and consuming digital media content across many sectors including publishing, education, entertainment, mobile and software. ODRL also supports protected digital content and honours the rights, conditions and fees specified for digital contents. It is important here that ODRL has been officially accepted by the Open Mobile Alliance as the standard rights expression language for all mobile content. OMA found that ODRL meets its requirements of a lightweight and simple language for expressing rights, easy to implement and optimized for delivery over constrained bearers (i.e. relatively slow and expensive connections like CSD or GPRS) and suitability for specifying rights independently of the content type and transport mechanism. ODRL is co-published with W3C (World Wide Web Consortium).

OMA DRM Enabler
In 2001 OMA started a Mobile DRM initiative. As a result, in 2002, the first version of the DRM enabler release was published. This set of specifications allows the expression of three interesting types of usage rights: the ability to preview DRM content, the ability to prevent DRM content from being illegally forwarded to other consumers, and to enable superdistribution of DRM content. It relies on the following DRM components, found in most DRM systems:
  • Rights Expression Language – DRMREL provides a concise mechanism for expressing rights over DRM content. It addresses requirements such as enabling preview of content, possibly prior to purchasing, expressing a range of different permissions and constraints, and optimization of rights objects delivered over constrained bearers. It is independent of the content being distributed, the mechanisms used for distributing the content, and the billing mechanisms used to handle the payments. DRMREL describes the structure of the rights expression language. The REL is defined as a mobile profile of ODRL.
  • Content Format – DRMCF was invented by OMA to define the content encoding for DRM protected encrypted media objects and associated metadata. The content format is intended to be used in the separate delivery DRM method.
Partial implementations of this first specification are to be found in some mobile phones by Motorola, Siemens, Nokia and Sony Ericsson, while the latter two have also full implementations, realizing all of the specified methods in their most recent top-of-the-line phones. Naturally several vendors support the server side of OMA DRM 1.0 with middleware solutions. This year OMA released the DRM 2.0 specification. The major difference is that while the earlier version provided basic protection functionalities for limited value content (e.g. ring tones, black&white logos, screensavers and Java games), the new specification adds trust and security mechanisms to enable protected distribution of high-value content (e.g. video clips, music and animated colour screensavers). The new enabler release is designed for future phones presuming enhanced device features and multimedia capabilities.

XrML – eXtensible rights Markup Language
XrML is a completely different breed than the OMA specifications. Based on years of research at Xerox Palo Alto Research Center, which invented the digital rights language concept, and backed by patented technology, XrML is currently governed by ContentGuard. The eXtensible rights Markup Language provides a universal method for securely specifying and managing rights and conditions associated with all kinds of resources including digital content as well as services. In XrML, rights and conditions can be securely assigned at varying levels of granularity to individuals as well as groups of individuals and the parties can be authenticated.
XrML is extensible and fully compliant with XML, and supports XML Signature and XML Encryption for authentication and protection of the rights expressions. Although currently controlled by a private company, XrML is going to be governed by the international standards community. It has already given input for MPEG-21, the OASIS Rights Language Technical Committee and the Open eBook Forum. Note however that both XrML and ODRL are, although freely available, using patented technologies, so implementing a new DRM system could infringe on intellectual property rights. The most powerful adopter of ContentGuard's XrML technology is Microsoft.

Bottom Line
With ODRL and XrML as the two most promising general purpose rights expression languages (others are IPMP by MPEG and XMCL by Real Networks), the standardization of DRM solutions has begun. A key difference between ODRL and XrML is that ODRL seems more applicable to actual transactions in the real media and publishing world, whereas XrML is more abstract and has designs for a broader spectrum of applications. Now there is a race of sorts between the two big standardisation efforts: XrML is the one being used in commercially deployed solutions, including the DRM solutions from Microsoft. ODRL is still in the game, notably with gains in the wireless world, where OMA has adopted it as rights-management language for mobile content. Nevertheless, while Microsoft may not be a key player in the mobile phone industry yet, its operating system for smart phones is gaining support among device developers not to mention their huge share in the handheld computer market. No doubt, it will be interesting to further watch competition of standards in the mobile field.


About the author: Kristóf Kerényi is a researcher at Budapest University of Technology and Economics in the SEARCH Laboratory. His interests include mobile and wireless IT security, as well as technological aspects of DRM. (Kerényi received a MSc in computer science from BUTE.) Contact:

Status: first posted 15/06/04; revised for INDICARE Monitor Vol. 1, No 1, 25 June 2004; licensed under Creative Commons