OMA DRM 2.0 Bibliographic Information

Note: The following OMA DRM 2.0 citations reference OMA draft version "in process" specifications. They are not yet approved Open Mobile Alliance specifications; the display documents are here used for educational purposes only. Updated draft and candidate versions may be available via the official OMA web site.

• DRM Rights Expression Language V2.0. Draft Version 2.0. 20-April-2004. Copyright (c) Open Mobile Alliance. Reference: 'OMA-DRM-REL-V2_0-20040420-D'. 42 pages. See the canonical version in .DOC format, distributed in the ZIP archive [cache]

• DRM Specification V2.0. Draft Version 2.0. 20-April-2004. Copyright (c) Open Mobile Alliance. Reference: 'OMA-DRM-DRM-V2_0-20040420-D'. 45 pages. See the canonical version in .DOC format, distributed in the ZIP archive [cache]

• Enabler Release Definition for DRM. Draft Version 2.0. 01-April-2004. Copyright (c) Open Mobile Alliance. Reference: 'OMA-ERELD-DRM-V2_0-20040401-D'. 13 pages. "This document outlines the Enabler Release Definition for DRM V2.0 and the respective conformance requirements for clients and servers implementing claiming compliance to it as defined by Open Mobile Alliance across the specification baseline." See the canonical version in .DOC format, distributed in the ZIP archive [cache]

• OMA DRM Requirements. Version 2.0. Version 15-May-2003. Copyright (c) Open Mobile Alliance. Reference: 'OMA-DRM-REQ-v2_0-20030515-C'. 21 pages. See the canonical PDF version.

• DRM Content Format V2.0. Draft Version 2.0. 20-April-2004. Copyright (c) Open Mobile Alliance. Reference: 'OMA-DRM-DCF-V2_0-200400420-D'. 32 pages. See the canonical version in .DOC format, distributed in the ZIP archive [cache]

• DRM Architecture. Draft Version 2.0. 15-March-2004. Copyright (c) Open Mobile Alliance. Reference: 'OMA-DRM-ARCH-V2_0-20040315-D'. 24 pages. Display version for educational purposes only. The Introduction provides a number of technical use cases including models for: Basic Pull Model; Push of DRM Content; Streaming of DRM Content; Domains; Backup; Super Distribution; Export; Unconnected Device Support. See the canonical version in .DOC format, distributed in the ZIP archive [cache]

Overview of the OMA DRM Rights Expression Language (REL)

OMA Digital Rights Management (OMA DRM 2.0) "defines the mechanisms to deliver DRM Content and Rights Objects to a consuming device. Rights are used to specify the access a consuming device is granted to DRM Content. The Rights Expression Language (REL) defined in DRM Rights Expression Language V2.0 specifies the syntax and semantics of rights governing the usage of DRM Content based on the Open Digital Rights Language (ODRL)." The OMA DRM 2.0 REL specification "defines [1] a subset, i.e., a mobile profile, of ODRL and [2] a data dictionary defining additional permissions and constraints beyond those provided by ODRL."

DRM Content is consumed according to the specified rights. Therefore, the value is in the rights and not in the Content itself. Rights Objects are specified so that they only become usable on authorized devices.

The goal of the DRM Rights Expression Language V2.0 specification is "to define a REL taking into account the special requirements and characteristics of the mobile domain to express consumption rights over DRM Content. Some of the specific goals include:

• Light-weight and simple way of expressing rights
• Lowering the entrance barrier for content providers and other players to adopt DRM technologies
• Suitable for specifying rights independently of the content type
• Suitable for specifying rights independently of the transport mechanism
• Enable specification of right to preview, i.e., test-drive, DRM Content enabling users to experience the Content first hand, possibly prior to purchasing it
• Enable specification of constraints to restrict permissions to the number of times Content can be accessed, and time limits and intervals during which Content can be accessed

"OMA Digital Rights Management release 2.0 defines a more comprehensive DRM system than release 1.0. The following are not goals of the REL: [1] To govern the distribution of DRM Content is not a goal of the REL. Since DRM Content is encrypted it is useless without the corresponding Rights Object, and thus there is no need for the REL to explicitly govern distribution. [2] To govern device management permissions such as 'install', 'uninstall', 'delete', etc. Freeing memory capacity on the device is an intrinsic right that every user has to his/her device."

In the OMA DRM rights expression language (REL), defined as a mobile profile of ODRL v1.1, rights "are the collection of permissions and constraints defining under which circumstances access is granted to DRM Content. The structure of the rights expression language enables the following functionality: Metadata such as version and content ID; The actual rights specification consisting of linking to and providing protection information for the content, and specification of usage rights and constraints."

"Models are used to group rights elements according to their functionality, and thus enable concise definition of elements and their semantics. The following models are used throughout the REL specification:

• Foundation model: The foundation model constitutes the basis for rights. It contains the <rights> element bringing together Meta information and agreement information. The foundation model serves as the starting point for incorporating the agreement model and the context model. The <rights> element is the root element of all Rights Objects defined according to this specification. It contains the mandatory <context>, and <agreement> elements linking assets to corresponding permissions.

• Agreement model: The agreement model expresses the Rights that are granted over an DRM Content. It consists of the <agreement> element connecting a set of Rights with the corresponding DRM Content specified with the <asset> element. The agreement model incorporates the permission model and the security model.

• Context model: The context model provides Meta information about the rights. It augments the foundation model, the agreement model, and the constraint model by expressing additional information. The <context> element is used in the <rights> element, in the <asset> element, and in the <individual> element. As the model's name already indicates, the semantics of its child elements depend on the context in which it occurs in the rights object.

• Permission model: The permission model augments the agreement model. It facilitates the expression of permissions over assets by specifying the access granted to a device. The permission model incorporates the constraint model allowing fine-grained consumption control of DRM Content. The set of permissions comprises <play>, <display>, <execute>, <print>, and <export>. Usage of the DRM Content MUST only be granted according to the permissions explicitly specified by the corresponding Rights Object(s). A permission that does not contain a <constraint> child element is unconstrained and access according to the respective permission element(s) MUST be granted.

  Note that the REL only specifies consumption and export rights and not management rights, e.g., install, uninstall, delete, or distribution rights. This is made possible by the separation of DRM Content and Rights Objects (although DRM Content and Rights Objects may be delivered together) freeing the REL from unnecessary complexity and overhead. Content can be stored; however, it can only be accessed if a corresponding Rights Object is available. Similarly, encrypted content can be super-distributed without unnecessarily complicating the REL; no separate distribution permissions are necessary, since DRM Content without the decryption key is of no value...

• Constraint model: The constraint model enhances the permission model by providing fine-grained consumption control of content. Constraints are associated with one permission element at a time. For a permission to be granted all its constraints MUST be fulfilled. If a constraint is not understood or cannot be enforced by the consuming device the parent permission is invalid and MUST NOT be granted. If present, a <constraint> element SHOULD contain at least one of its child elements. If a <constraint> element does not contain any constraints such as <count>, <datetime>, etc. it is unconstrained, and a DRM Agent MUST grant unconstrained access according to the permission containing such an unconstrained <constraint> element...

• Inheritance model: The Inheritance model section describes how a parent Rights Object can specify Permissions and Constraints for one or more pieces of DRM Content each governed by a child Rights Object, using a limited subset of the ODRL inheritance model. The DRM Agent MUST NOT accept parent child Rights Objects constellations with more than one level of inheritance (i.e., parent-child). In other words, a parent Rights Object MUST NOT inherit Permissions and Constraints from another Rights Object...

• Security model: Security constitutes an important part of a DRM system. OMA DRM 2.0 provides confidentiality for the CEK of Rights Objects, integrity of the association between Rights Objects and DRM Content, and Rights Object integrity and authenticity... Rights Objects defined in this specification MUST be contained in a <ProtectedRO> element as defined in DRM Specification V2.0 to protect against unauthorized Rights Issuers, or Rights Object replay. The ODRL security model, which forms the basis for the security model of this specification, is based on [the W3C] XML Encryption Syntax and Processing and [W3C/IETF] XML Signature Syntax and Processing..." [provisional text from the draft version of 2004-04-20]

Highlights of OMA DRM 2.0

Dr. Willms Buhse (Vice Chair, OMA Download and DRM Group; CoreMedia) presented a Keynote "OMA Secure Content Delivery for the Mobile World" at the ODRL International Workshop 2004 in Vienna, Austria, Friday 23 April 2004. This presentation is available online, together with other papers and workshop transcripts. Slides 6-8 in the presentation of Willms Buhse summarize key features of OMA DRM 2.0:

OMA DRM 2.0 for Premium Content

• DRM solution is evolving with the mobile industry
  • High bandwidth cellular networks becoming widely available
  • Mobile devices with removable media and larger color screens support downloading and streaming rich media
  • Content and service providers eager to release rich audio/video content and applications
• Greater security and trust management required to protect high value content
  • Need to ensure target device can be trusted to keep content and trade secrets safe
  • Need greater security to prevent content from leaking out during distribution

OMA DRM 2.0 Benefits for Content Providers

• Enhanced security
  • Individually encrypted rights object using device's public key to provide cryptographic binding (to SIM/WIM)
  • Integrity protection for content and rights objects
• Explicit trust mechanisms
  • Mutual authentication between device and rights issuer
  • Device Revocation: Rights issuer can identify device revocation status
• Secure multicast and unicast streaming
  • Working with 3GPP and 3GPP2 on packetised file format for protected streaming and progressive download
• Wide variety of business models
  • Metered time and usage constraints
  • Subscription rights for content bundles
  • Gifting
• Support for Peer-to-Peer and Messaging
  • SuperDistribution: Viral marketing and reward mechanism

OMA DRM 2.0 Benefits for End Consumers

• Advanced content management
  • Storage and backup: move content and rights to remote or removable storage and later restore to device
  • Multiple devices: Move content and rights objects easily between several devices owned by a user (2nd phone)
• Sharing between multiple user within domain
  • Domain concept for sharing between devices in the same domain (e.g., family)
• Unconnected devices
  • Copy to SD card for a mobile music player
• Complementary Preview
  • Constraints for superdistributed content before purchase
• Export to other copy protection schemes
  • Transfer music to DRM-enabled Settop box or computing device

Overview of OMA Digital Rights Management

"The OMA Browser and Content Working Group (BAC) is responsible for the specification of application technologies used in the open mobile architecture. BAC is specifically chartered to be responsible for base content types, including the semantics and such user agents, behaviour and programming interfaces as is necessary to use such content types, render them and interact with the browser user agent, with the intention of enabling the creation and use of data services on mobile hand held devices, including mobile telephones, pagers and PDAs...

The goal of the Browser and Content Working Group (BAC) Download and DRM is to specify application level protocols and behaviors that provide transactional and life cycle management of content and applications on mobile devices. Examples include: confirmed content delivery; support charging for content delivery and use; protection of personal and commercial content; constraining content usage based on associated permissions; content distribution, including super-distribution; support for storing and sharing content and applications..."

"The scope of 'OMA Digital Rights Management' is to enable the controlled consumption of digital media objects by allowing content providers the ability, for example, to manage previews of DRM Content, to enable superdistribution of DRM Content, and to enable transfer of content between DRM Agents. The OMA DRM specifications provide mechanisms for secure authentication of trusted DRM Agents, and for secure packaging and transfer of usage rights and DRM Content to trusted DRM Agents.

A Rights Object governs how DRM Content may be used. It is an XML document specifying permissions and constraints associated with a piece of DRM Content. DRM Content cannot be used without an associated Rights Object, and may only be used according to the permissions and constraints specified in a Rights Object...

There is a growing need for a rights management system in the mobile industry so that the operators and content providers can make digital content available to consumers in a controlled manner. Digital Rights Management is a set of technologies that provide the means to control the distribution and consumption of the digital media objects. OMA has already published release 1 of the DRM specifications. The release 1 specifications provide some fundamental building blocks for a DRM system. But, they lack the complete security necessary for a robust, end-to-end DRM system that takes into account the need for secure distribution, authentication of Devices, revocation and other aspects. This specification addresses these missing aspects of the OMA DRM.

The OMA DRM enables content providers to grant permissions for media objects that define how they should be consumed. The DRM system is independent of the media object formats and the given operating system or run-time environment. The media objects controlled by the DRM can be a variety of things: games, ring tones, photos, music clips, video clips, streaming media, etc. A content provider can grant appropriate permissions to the user for each of these media objects. The content is distributed with cryptographic protection; hence, the Protected Content is not usable without the associated Rights Object on a Device. Given this fact, fundamentally, the users are purchasing permissions embodied in Rights Objects and the Rights Objects need to be handled in a secure and uncompromising manner.

The Protected Content can be delivered to the Device by any means (over the air, LAN/WLAN, local connectivity, removable media, etc.). But the Rights Objects are tightly controlled and distributed by the Rights Issuer in a controlled manner. The Protected Content and Rights Objects can be delivered to the Device by downloading them together, or by sending them separately. The system does not imply any order or 'bundling' of these two objects. It is not within the scope of the DRM system to address the specific payment methods employed by the Rights Issuers.

OMA DRM 2.0 consists of a set of specifications developed by OMA to address the need for digital rights management... The OMA DRM Version 2.0 specification defines the format and semantics of the cryptographic protocol, messages, processing instructions and certificate profiles that will, together enable an end-to-end system for protected content distribution. This includes the Rights Object Acquisition Protocol messages, the Key Management protocols, the domains functionality (sharing of content and rights among a set of Devices enrolled into a Domain), super distribution, transport mappings for ROAP, binding rights to user identities, and exporting to other DRMs, the certificate profiles, and application to other services like MMS and streaming..." [adapted from the Architecture and Enabling Release documents, with the BAC description]

OMA DRM 2.0 Enabler Release Announcement and Commentary

From the OMA Announcement

In an ongoing effort to accelerate the wireless industry's adoption of rich and accessible mobile services, the Open Mobile Alliance (OMA), an industry organization delivering specifications for interoperable mobile service enablers across the world, today announced the release of the OMA DRM 2.0 Enabler Release, designed to protect high-value content produced and distributed by a wide range of content and service providers.

"OMA is helping the entertainment and media industries deliver premium content to millions of mobile consumers in a trustworthy and secure way," said Willms Buhse, vice chair of OMA's DRM Working Group. "Our upgraded enabler release reinforces the high priority of DRM within OMA, and underscores the importance of content and copyright protection when using mobile devices. As trust and security improves, the industry will benefit from significant revenue enhancement opportunities through offering rich content through pervasive mobile access."

For handsets and other mobile devices, the enhanced OMA DRM 2.0 Enabler Release represents the next step in pervasive mobile access. While the OMA DRM 1.0 Enabler Release, issued in November 2002, provides the basic protection functions for limited value content, OMA DRM 2.0 with its added trust and security illustrates how OMA has enhanced the functionality of the specification to address the needs and principal concerns of content providers.

The new enabler release takes advantage of expanded device capabilities and offers improved support for audio/video rendering, streaming content and access to protected content using multiple devices, thus enabling new business models.

OMA, formed in June 2002 and now comprising of nearly 350 member companies involved with mobile services technology, unveiled the OMA DRM 2.0 Enabler Release at its 'OMA Secure Content Delivery for the Mobile World' event today, held in conjunction with OMA's Technical Plenary meeting in Los Angeles. More than 150 DRM professionals are attending the event, including leading content providers, applications developers, server-and-device vendors, and mobile operators. Guest panelists include executives from Universal Music, Sony Music and Bitfilm.

Commentary by Bill Rosenblatt

Excerpt from DRM Watch, "Open Mobile Alliance Announces Version 2.0 of DRM Standard," by Bill Rosenblatt:

"The Open Mobile Alliance (OMA) announced on Monday the impending release of version 2.0 of its DRM standard for mobile devices (OMA DRM 2.0). The OMA expects to release the specification during the first half of this year. At the same time, the Content Management License Administrator (CMLA), a consortium whose members span device makers, software vendors and content providers, announced its intention to build a licensing authority as well as a technical and legal trust foundation for OMA DRM 2.0 in time to build into devices that would be available for the 2004 year-end holiday season.

OMA DRM 2.0 adds two primary elements to OMA DRM 1.0's security model. One is public-key encryption for protecting the symmetric keys used to encrypt content - a feature that is common in DRM technologies for PCs. Another is a scheme - yet to be specified, but probably digital certificates or cryptographic digests - for ensuring the integrity of the content itself. A third added security element, the ability to authenticate devices, is up to the CMLA...

The new standard also adds the ability to support richer content business models, such as stateful rights (e.g., play N times) and, more significantly, the ability to copy content to other devices that a person owns, including backup storage. Definitions of problematic concepts like 'device ownership' and 'backup' are left to implementers; of course, content owners are free to grant such rights or not, as they choose. These business models are expressible in OMA DRM 2.0's rights expression language (REL), which — as before — is based on a subset of ODRL from IPR Systems.

The CMLA, formerly known as Project Hudson, is a complementary effort to OMA DRM 2.0. Its membership includes companies that span the entire content value chain, from content (Warner Bros. film studios) to wireless carriers (mmo2) to chips (Intel) to devices (Nokia, Matsushita, Samsung) to software (RealNetworks). Its primary purpose is to establish a trust model on which to base OMA DRM implementations — that is, a framework for allowing devices to communicate their authenticated identities to content services as well as to ensure that those devices are impervious to being spoofed (e.g., the identities copied and misused by a third party) or tampered with (e.g., so that perfect cleartext copies of digital content can be made from them).

To do this, the CMLA has to establish key and digital certificate distribution services, compliance rules and testing tools for vendors to use to ensure that their devices are trustworthy, and legal backstops for devices that are either noncompliant or hacked.

Many vendors of devices, client software, and server software are jumping on this very fast-moving bandwagon. Software vendors that have announced intention to implement OMA DRM 2.0 include RealNetworks, Lockstream, Sun Microsystems (through its Pixo acquisition), NDS, OpenWave, Germany's CoreMedia, and the Netherlands' DMDSecure. (Microsoft is a member of the working group but has not announced intent to launch any compatible products.) Most of the prominent mobile device makers have also pledged support, and already there are over 50 mobile devices on the market that are OMA DRM 1.0 compatible.

The breathtaking rapidity with which OMA DRM is progressing in the market, compared to other DRM-related standards initiatives, arises from one primary factor: mobile devices' simplicity and relative immaturity as content-rendering devices, compared to PCs and other more complex content-rendering form factors. The modest profile of the target devices for OMA DRM 1.0 implied that the spec should also be very modest, allowing only a narrow range of content distribution models. That, in turn, made the OMA DRM 1.0 spec something that could be finalized and moved into the market very quickly..."

Open Digital Rights Language (ODRL)

About ODRL

ODRL was selected by the Open Mobile Alliance as the basis for OMA DRM Rights Expression Language in OMA DRM 1.0 and OMA DRM 2.0. The Open Digital Rights Language (ODRL) Initiative is "an international effort aimed at developing and promoting an open standard for the Digital Rights Management expression language."

The ODRL specification "supports an extensible language and vocabulary (data dictionary) for the expression of terms and conditions over any content including permissions, constraints, requirements, conditions, 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 of digital media across all sectors including Publishers, Education, Entertainment, Mobile, and Software, ODRL also supports protected digital content and honours the rights, conditions and fees specified for digital contents.

The ODRL Initiative believes strongly in the benefits of free and open standards to the wider community. As a result, all ODRL specifications are available without any obligations and have no licensing requirements. This is in the spirit of the 'open source' community..." [overview brochure]

Library of Congress Report on Rights Expression Languages

On May 20, 2004 Sally H. McCallum of the Network Development and MARC Standards Office, US Library of Congress posted an announcement for the release of a published report on leading rights expression languages, including ODRL.

"The report was commissioned by the Library's Network Development and MARC Standards Office to help establish a methodology for examining emerging rights languages. It is a contribution to the information community dialog on issues and tools for controlling digital rights. The study compares four major languages — MPEG21/5, ODRL, Creative Commons, and METSRights — plus a few others, and establishes a taxonomy of characteristics to consider when selecting a language for a particular application. The report is also useful to clarify thinking on directions that need to be pursued in new rights expression language developments over the next few years. Rights management in the digital arena is a fast moving target, as is exemplified by the recent changes in ownership of XrML..." (posted to the Metadata Encoding and Transmission Standard List)

From the Executive Summary of Karen Coyle's Rights Expression Languages: A Report for the Library of Congress

"The goals and purposes of the RELs are characterized as expression of copyright, expression of contract or license agreements, and control over access and/or use. An understanding of these different purposes can be used to explain many of the differences between these and other RELs. In particular, the degree to which RELs are intended to be machine-actionable is a determinant in the kinds of rights that can be expressed in the REL...

Although the main contenders for a generalized REL today appear to be MPEG-21/5 (based on XrML) and ODRL, this doesn't mean that one is limited to choosing between these two. The only prevailing wisdom is that there is not (and probably will never be) a universal REL, any more than there will be a universal metadata format. This is especially the case because a rights expression language exists in the context of a larger system and the nature of that larger system and its requirements determine the features needed in the REL.

The main purpose of this paper is to expose the underlying goals and assumptions of a range of existing rights expression languages, and to establish a taxonomy that will allow us to evaluate RELs in relation to sets of requirements. This taxonomy may also aid in the further development of languages that serve specific or general needs.

To do the necessary analysis, four representative RELs have been chosen that cover a wide range of the functions and goals of rights expression. Not only do they vary greatly in the number of elements in the language and the degree of encoding that these elements receive, each also has its own context and it is necessary to include this context in our analysis of the REL...

The author notes in the section 'Business Models of Rights Expression Languages' that the RELs analyzed are "significantly different from each other in terms of their business models — that is, in terms of how they themselves can be licensed and used." Three of the four RELs studied have no license requirements for use: Open Digital Rights Language (ODRL), Creative Commons, and METSRights (METSR). They are open specifications, delivered patent-free by their designers, and are freely downloadable on the Internet. MPEG-21/5 must be purchased from ISO; it is based upon the legally encumbered (patented) XrML(TM) from ContentGuard, recently acquired by Time Warner and Microsoft.

Principal References

• Open Mobile Alliance (OMA):
  • Announcement: "Open Mobile Alliance Takes Critical Next Step In Delivering Premium Content to Consumers Via Wireless Media Devices. OMA Issues Version 2.0 of its Digital Rights Management Enabler Release." [source]
  • OMA DRM 2.0 Bibliographic Information. Citations for the six key documents in the OMA DRM 2.0 Enabler Release are listed above.
  • OMA Browser and Content Working Group (BAC), and its Download and DRM Sub-workgroup
  • Permanent documents of the OMA BAC DLDRM group
  • "OMA Secure Content Delivery for the Mobile World." By Dr. Willms Buhse (Vice Chair, OMA Download and DRM Group; CoreMedia). ODRL Workshop, Vienna, Austria. Presented at the ODRL 2004 Workshop; see paper citations in the program listing. The presentation covers: OMA Digital Rights Management background; OMA DRM v1 for light media; New DRM v2 for premium content; Benefits for content providers; Benefits for end consumers; Applying OMA DRM to protect content. "OMA's DRM is a response to the need for a mass market solution: Timely and inexpensive to deploy; For mass market mobile devices (not just high-end); Did not require costly infrastructure to be rolled out..."
  • "Digital Rights Management for Interoperable Mobile Services. How the Open Mobile Alliance Enables Increased Revenues for Handset Vendors and Mobile Operators." By Willms Buhse (CoreMedia). In Wireless Business and Technology Volume 4, Issue 3 (September/October 2004). See the excerpt.
  • "Open Mobile Alliance: Digital Rights Management." Short paper. December 2003. Describes OMA DRM version 1.0 Enabler Release and interoperability testing.
  • Open Mobile Alliance Announces Version 2.0 of DRM Standard." By Bill Rosenblatt. In DRM Watch.
  • OMA Members. "Since its inception in June 2002, the Open Mobile Alliance has grown to more than 300 companies representing mobile operators, device and network suppliers, information technology companies, and content providers."
  • OMA Release Program and Specifications
  • Open Mobile Alliance (OMA) web site
• ODRL:
  • ODRL Initiative web site
  • ODRL International Workshop 2004. The online Program Listing provides references for the workshop presentations.
  • Open Digital Rights Language (ODRL). Version: 1.1.
  • "A Formal Foundation for ODRL." By Riccardo Pucella and Vicky Weissman. Presented at the Workshop on Issues in the Theory of Security (IFIP WG 1.7, WITS 2004). "Languages for writing agreements typically fall into one of three categories: native languages, such as English, that cannot be interpreted by machines, XML-based languages that enjoy popular support by application writers, and formal logics that are endorsed by computer scientists, because they have formal semantics (no ambiguity) and are tractable (queries can be answered typically in a low-order polynomial time). ODRL belongs to the second category. By providing formal semantics to a fragment of ODRL, we get the benefit of using a formal approach, namely no ambiguity, and we can begin to search for a tractable fragment. In this way, we get the best of both worlds."
  • ODRL Implementations. Examples as of 2003-10-17.
  • Earlier news:
    • "ODRL International Workshop 2004 Call for Participation." News story 2003-10-17.
    • "RoMEO and OAI-PMH Teams Develop Rights Solution Using ODRL and Creative Common Licenses." News story 2003-09-26.
    • "Open Digital Rights Language (ODRL) Specification Submitted to W3C." News story 2002-09-24.
    • "Proposed Open Mobile Alliance (OMA) Rights Expression Language Based Upon ODRL." News story 2002-08-12.
  • "Open Digital Rights Language (ODRL)" - Main reference page.
• Rights Expression Languages: A Report for the Library of Congress. By Karen Coyle. Commissioned by the US Library of Congress, Network Development and MARC Standards Office. February 2004. 53 pages. [cache]
• Creative Commons. See the description of machine-readable CC licenses. Also: local references.
• Metadata Encoding and Transmission Standard (METS). See the Draft Rights Declaration Schema overview and XML schema instance.
• "XML and Digital Rights Management (DRM)" - Main reference page.