addressing metadata in the mpeg-21 and pdf-a iso standards niso workshop: metadata on the cutting...

Addressing Metadata in the MPEG-21 and PDF-A ISO StandardsNISO Workshop: Metadata on the Cutting EdgeMay 2004

William G. LeFurgyU.S. Library of [email protected]

MPEG-21 and PDF-A Metadata 2NISO Workshop, May 2004

Presentation Overview

• Outline metadata approaches in two developing International Organization for Standardization specifications:– MPEG-21 (ISO 21000)– PDF-A (ISO 19005)

• Highlight some practical advantages and disadvantages of both

• My personal views, not those of LC


Issues to Keep in Mind

• Specs are in process: parts of MPEG-21 await initial approval; PDF-A is not yet approved

• Limited implementation experience• Different communities have not yet

compared different standards in detail• Landscape is sure to change over next

several years


MPEG Background• Series of standards from Moving Picture

Experts Group• MPEG-1, -2: Coding methods to compress

A/V streams (DVD, digital TV, MP3 audio)• MPEG-4: Compression plus ability to interact

with A/V objects (Quicktime 6, iTunes AAC)• MPEG-7: Standard way to represent/bundle

multimedia objects using XML; useful for indexing, searching, distributing content


MPEG-21 Overview• Builds on MPEG-7 use of XML to

define/constrain/bundle multimedia objects (text, video, audio, etc.)

• Also defines how any kind of user can interact with content

• A comprehensive framework to enable interoperable but controlled use of content from creation, distribution, and consumption

• Protection of commercial IP rights is central


MPEG-21 Features

• Multiple modular parts• Part 2, Digital Item Declaration Language

(DIDL) uses XML to express content elements, e.g.: – Container (items grouped as a logical package)– Item (a logical work)– Statement (descriptive, administrative metadata)

• Part 3, Digital Item Identification states how to link unique identifiers to items


From: http://www.chiariglione.org/mpeg/standards/mpeg-21/image004.gif


MPEG-21 Rights Expression Language • Part 5, Details “machine readable

language to declare rights and permissions”

• Aims to support end-to-end interoperability with access and use controls

• Uses ContentGuard/Microsoft XrML (Extensible Rights Markup Language) spec


The REL Data Model

From: http://www.chiariglione.org/mpeg/standards/mpeg-21/image008.gif


Digital Repositories and MPEG-21• Los Alamos National Laboratory uses spec to

represent and manage complex digital objects • Serves to package objects for repository

submission, storage, and dissemination as outlined in OAIS model

• Accommodates existing metadata records and enables capture of life cycle management metadata

• Also used in conjunction with NISO OpenURL and OAI-PMH


MPEG-21 Pros and Cons• Pro

– International standard– Broad commercial support for earlier MPEG specs– Packages any type of complex digital object per OAIS– Powerful and flexible means to express descriptive,

structural, administrative, and other metadata

• Con– Complex and highly technical– Few tools currently exist– Unclear now the extent to which spec will be adopted– Strong emphasis on commercial rights protection?


PDF-A Background

• Goal is to define use of Adobe PDF version 1.4 for long-term preservation purposes

• Effort stems from extensive use of PDF as primary format for records and documents that require long-term retention

• Standard is being developed by ISO working group with representatives from government, industry, academia


PDF-A Overview• Defines a constrained version of PDF that

should remain viable for many years:– Audio and video content are forbidden – Javascript and executable file launches are prohibited – All fonts must be embedded and also must be legally

embeddable for unlimited, universal rendering – Colorspaces specified in a device-independent manner – Encryption is disallowed

• Requires a standards-based approach to metadata


PDF-A Metadata Features• Based on Adobe Extensible Metadata

Platform (XMP)• XMP is based on Resource Description

Framework (RDF) and XML specifications• Adobe has defined core schemas

(descriptive, media management, rights management, etc.)

• XMP permits broad extensibility for defining customized schemas

• Provides for embedding XML text packets in binary PDF files


Digital Repositories and PDF-A

• Not yet tested in a repository context…• …But repositories are (or will soon be)

rife with PDF files from e-government, online publishing, and business workflow activities

• PDF-A addresses conceptual repository needs for a stable file format with rich descriptive and administrative metadata


PDF-A Pros and Cons• Pro

– International standard (pending)– Broad commercial support for Adobe PDF spec– Meets many user needs across the digital life cycle – Powerful and flexible means to express descriptive and

administrative metadata

• Con– Complex and highly technical– Few tools currently exist– Unclear now the extent to which spec will be adopted– XMP limitations for validating metadata– Requires another standard to package items per OAIS


Further Information: MPEG-21• MPEG-21 Overview v.5: http://www.chiariglione.org/mpeg/standards/mpeg-21/mpeg-21.htm

• Using MPEG-21 DIDL to Represent Complex Digital Objects in the Los Alamos National Laboratory Digital Library

http://tinyurl.com/22e65

• Using MPEG-21 DIP and NISO OpenURL for the Dynamic Dissemination of Complex Digital Objects in the Los Alamos National Laboratory Digital Library http://tinyurl.com/2klwz

• From MPEG-1 to MPEG-21 http://tinyurl.com/3brc8


Further Information: PDF-A• PDF-A Committee web site:

http://www.aiim.org/standards.asp?ID=25013

• PDF-A: Developing a File Format for Long-Term Preservation

http://www.rlg.org/preserv/diginews/diginews7-6.html#feature1

• Adobe XMP web site http://www.adobe.com/products/xmp/main.html

addressing metadata in the mpeg-21 and pdf-a iso standards niso workshop: metadata on the cutting...

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