Overview
ISO/IEC 21000-5:2004 is Part 5 of the MPEG-21 multimedia framework and specifies the syntax and semantics of a Rights Expression Language (REL). The standard defines how to represent rights, licenses and authorization rules in a machine-readable form (including XML conventions and namespaces) and provides an authorization model to evaluate whether a given Principal may perform a specified Right on an optional Resource within an authorization context and trusted root. It does not grant legal permissions, prescribe security mechanisms, mandate accounting systems (monetary/state transactions), or dictate when rights must be consulted.
Key topics and technical requirements
- Rights Expression Language (REL) syntax and semantics: canonical structures for encoding licenses, grants and related metadata.
- Authorization model: formal model for evaluating authorization requests against rights expressions, contextual properties and trust roots.
- Core elements (as defined in the standard): License, Principal, Right, Resource, Condition, TrustRoot, LicenseGroup, DelegationControl, EncryptedContent, and more.
- Authorization context: rules and environmental data used when deciding whether an action is permitted.
- License semantics: how grants, revocation, validity intervals, delegation and derived grants behave semantically.
- XML conventions and namespaces: structural notation conventions to ensure consistent REL encoding and interoperability.
- Extensibility: a standard extension framework for additional principals, rights, conditions and service descriptions.
- Security and revocation concepts: support for revocable grants and encrypted elements (note: the standard does not prescribe specific security implementations).
Practical applications
- Encoding and exchanging machine-readable licenses and usage policies for digital media.
- Implementing policy engines or DRM components that evaluate user requests against formal rights expressions.
- Enabling consistent interoperability between content providers, service platforms, devices and archives using MPEG-21 REL.
- Modeling delegation, revocation, time-limited access and conditional consumption for streaming, download, enterprise content and library systems.
- Providing a base language for enterprise content management, digital libraries, multimedia distribution platforms and licensing services.
Who should use this standard
- DRM system architects and implementers
- Content providers, aggregators and distributors
- Software and device manufacturers implementing license enforcement
- Platform developers building authorization and policy evaluation engines
- Digital library and archive system designers
- Standards and compliance teams working with MPEG-21 ecosystems
Related standards
- ISO/IEC 21000 (MPEG-21) family - other parts address architecture, digital item declaration and related multimedia framework components. Use ISO/IEC 21000-5 in conjunction with other MPEG-21 parts for full multimedia rights management solutions.
Keywords: ISO/IEC 21000-5, MPEG-21, Rights Expression Language, REL, digital rights, DRM, authorization model, license syntax, XML rights expressions, trust root.
Open preview (PDF)Information technology — Multimedia framework (MPEG-21) — Part 5: Rights Expression Language
