Overview
ISO/IEC 15938-2:2002 - part of the MPEG‑7 family - specifies the Description Definition Language (DDL) for a standardized multimedia metadata system. The DDL defines how to create, constrain and validate Description Schemes (DS), Descriptors (D) and reusable datatypes used to describe audio, visual and multimedia content. Built on W3C XML Schema with MPEG‑7 specific extensions, this standard enables interoperable, machine- and human‑readable metadata for indexing, searching, synchronizing and exchanging multimedia assets.
Key topics and technical requirements
- Description Definition Language (DDL): normative specification of DDL constructs, syntax and datatypes to define DS and D.
- XML Schema foundation: adopts W3C XML Schema (Parts 0/1/2) and extends it with MPEG‑7 specific structural and datatype components; Annex C contains the normative MPEG‑7 extensions.
- Datatypes and descriptors: defines primitive and composite datatypes (e.g., integers, text, histograms, enumerations) used by descriptors.
- Structural modelling: supports expression of spatial, temporal, structural and conceptual relationships between description elements and between descriptions and multimedia data.
- Validation and tooling: DDL is intended to enable development of editors, parsers and validators that can check DS/Ds and instantiate descriptions.
- Extensibility: language allows refinements, extensions and modifications to adapt to new application needs.
- Interoperability requirements: must be platform- and application‑independent, and align with related standards (ISO 8601, ISO 639, ISO 3166, MIME types, RDF influences).
Practical applications
- Metadata schema design for multimedia asset management, digital libraries and archives.
- Creation of interoperable descriptors for content indexing, search engines, and recommendation systems.
- Tooling: DDL-based editors, schema validators, parsers and converters for content ingestion pipelines.
- Broadcast, streaming and synchronization: attaching rich descriptions to media for timed metadata, closed-captioning indexing, and content-aware transport/multiplexing.
- Research and development of content-analysis algorithms that output standardized MPEG‑7 descriptions.
Who should use this standard
- Multimedia standards engineers and metadata architects designing DS and descriptor vocabularies.
- Software developers building metadata editors, validators, parsers and media management systems.
- Broadcasters, streaming platforms, digital asset managers and archives that require interoperable multimedia metadata.
- Research labs and companies developing content analysis, indexing and search technologies.
Related standards
- ISO/IEC 15938 (MPEG‑7) - Parts 1–8 (Systems, Visual, Audio, MDS, Reference software, Conformance, Extraction/use)
- W3C XML Schema (Parts 0/1/2) and XML 1.0
- RDF (influence on linking and references)
- ISO 8601, ISO 639, ISO 3166, ISO 4217, MIME/RFCs
Keywords: ISO/IEC 15938-2, MPEG‑7 DDL, multimedia metadata, description schemes, descriptors, XML Schema, MPEG‑7 extensions, multimedia indexing.