Addressing Metadata in the MPEG-21 and PDF-A ISO Standards NISO Workshop: Metadata on the Cutting Edge May 2004 William G. LeFurgy U.S. Library of Congress [e-mail]

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Addressing Metadata in the MPEG-21 and PDF-A ISO
StandardsNISO Workshop Metadata on the Cutting
EdgeMay 2004William G. LeFurgyU.S. Library of
Congresswlef_at_loc.gov
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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

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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

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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

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MPEG-21 Overview

• Builds on MPEG-7 use of XML to define/constrain/bu
  ndle 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

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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

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

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The REL Data Model
From http//www.chiariglione.org/mpeg/standards/m
peg-21/image008.gif
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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

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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?

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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

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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

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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

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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

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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

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Further Information MPEG-21

• MPEG-21 Overview v.5
• http//www.chiariglione.org/mpeg/standards/mp
  eg-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

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Further Information PDF-A

• PDF-A Committee web site
• http//www.aiim.org/standards.asp?ID25013
• PDF-A Developing a File Format for Long-Term
  Preservation
• http//www.rlg.org/preserv/diginews/diginews7-
  6.htmlfeature1
• Adobe XMP web site
• http//www.adobe.com/products/xmp/main.html