Dublin Core Metadata Tutorial July 9, 2007 Stuart Weibel Senior Research Scientist OCLC Programs and Research

1
Dublin Core Metadata TutorialJuly 9,
2007Stuart WeibelSenior Research
ScientistOCLC Programs and Research
2
Tutorial Roadmap

• Principles of Metadata
• Dublin Core Metadata Basics
• The Dublin Core Abstract Model
• Syntax Alternatives for DC Metadata
• Mixing and Matching Metadata
• History and workings of the Dublin Core Metadata
  Initiative
• Acknowledgements I have borrowed liberally from
  tutorial slides sets from Tom Baker, Diane
  Hillman, Andy Powell, and Marty Kurth, available
  at Dublincore.org

3
Basic Principles of Metadata

• The Web as an information system
• The Internet Commons
• Interoperability is key
• MARC lives
• The varieties of metadata
• Modularity
• Some Challenges

4
State of the Web as an Information System

• Search systems are motivated by business models,
  not functionality
• Index coverage is broad, but unpredictable
• Too much recall, too little precision
• Index spam abounds
• Resources (and their names) are volatile
• What about versions, editions, back issues?
• Archiving is presently unsolved
• Authority and quality of service are spotty
• Managing Intellectual Property Rights is
  difficult

5
Metadata Part of a Solution

• Structured data about other data
• helps to impose order on chaos
• enables automated discovery/manipulation
• Full Text Web indexing is the dominant idiom for
  search
• Metadata is more useful in structured
  collections, used in combination with
  applications designed to take advantage of
  structured descriptions

6
Internet Commons includes Multiple Communities
7
Interoperabilityrequires conventions about

• Semantics
• The meaning of the elements
• Structure
• human-readable
• machine-parseable
• Syntax
• grammars to convey semantics and structure

8
Havent we done metadata already?
The MARC family of standards is the single most
successful resource description standard in the
world
9
MARC Cataloging

• Is really MARC-AACR2 cataloging
• MARC is the communications format
• AACR2 (Anglo-American Cataloging Rules) defines
  the cataloging rules (semantics
• MARC and AACR2 are evolving
• Closer alignment with XML as a syntax option
• RDA is an effort to modernize AACR2, and
  alignment it with networked environments
• RDA and Dublin Core are cooperating on alignment
  of a common underlying data model.

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Whats wrong with this model on the Web?

• Expensive
• Complex
• Professional Catalogers required
• Bias towards bibliographic artifacts
• Fixed resources
• Incomplete handling of resource evolution and
  other resource relationships
• Anglo-centric
• MARC 21 accounts for ¾ of MARC records, but there
  are many other varieties

11
Metadata Takes Many Forms
12
Warwick Framework Modular Metadata

• Conceptual Architecture for metadata from the
  Warwick Metadata Workshop (DC-2)
• Conceptual architecture to support the
  specification, collection, encoding, and exchange
  of modular metadata
• Provide context for metadata efforts (including
  Dublin Core)
• avoids the black-hole of comprehensive element
  sets
• focuses interoperability issues at package level
• A conceptual framework, NOT an application

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Modularity and Extensibility the Lego metaphor

• DC is a beginning, not an end
• An architecture for modular, extensible metadata
• The simplest common denominator
• Add stuff you need for
• Local requirements
• Domain specific functionality
• Other dimensions of description
• Eg cloud cover management structural metadata.

14
Descriptive Metadata Standards

• IEEE LOM (Learning Object Metadata)
• Descriptive and structural metadata to support
  instructional systems
• ONIX (Online Information Exchange) bookseller
  metadata
• FGDC Federal Geographic Data Committee rich
  descriptive and structural metadata for GIS
  applications
• Encoded Archival Description description of
  archival collections
• MPEG Multimedia Metadata large, complicated,
  still in progress descriptive, structural,
  rights management
• Dublin Core core descriptive metadata

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Metadata Creation

• Metadata is expensive and error prone
• A MARC Record costs about 100 USD to create one
  record at the Library of Congress
• Competes with indexing at 00.001 ???
• Capture it as close to point of creation as
  possible
• Capture as much automatically as possible
• Should be designed with close attention to the
  functional requirements it serves
• Re-use existing standards whenever possible
• Always tension between completeness of
  description, intended purpose, and cost

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Metadata Challenges

• Accommodate multiple varieties of metadata
• Tension functionality and simplicity
• Tension extensibility and interoperability
• Human and machine creation and use
• Community-specific functionality, creation,
  administration, access work at cross purposes to
  global interoperability

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Interoperability barriers cost time and moneyA
Common data model helps avoid this
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Dublin Core Basics

• Design Philosophy useful metaphors
• Language and pidgins
• Characteristics of DC metadata
• The simple bucket (properties)
• Resource Types
• Metadata grammar
• Dublin Core Principles
• One-to-one
• Dumb-down rule
• Context appropriate values
• Translations

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Dublin Core Starting Assumptions and Essential
Features

• Simple
• true to a point the elements are simple, the
  underlying model is not
• Consensus-based
• Crucial to early success, both in attracting
  expertise and deployment. Bottom up
• Based on the experience of practitioners, but
  hard to capture and capitalize on lessons learned
• Cross-disciplinary and International
• Central success factor

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Essential Features (continued)

• The Web is the strategic application
• On the mark
• International
• Also central success factor, but hard (20
  languages in the Registry)
• Lego-like modularity extensibility
• Partially realized promise
• Application Profiles are the means
• Syntax independence
• An ongoing nightmare (HTMLXMLRDF/XML)
• Authors will describe their own works
• Laughably naïve

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A Pidgin for Digital Tourists

• Metadata is language
• Dublin Core is a small and simple language -- a
  pidgin -- for finding resources across domains
• Speakers of different languages naturally
  "pidginize" to communicate
• E.g., tourists using simple phrases to order beer
  ("zwei Bier bitte" "dva pivo" "biru o san
  bai"...)
• We are all "tourists" on the Internet.

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A Grammar of Dublin Core

• By design not as rich as mother tongues, but easy
  to learn and useful in practice
• Pidgins small vocabularies (Dublin Core fifteen
  special nouns and lots of optional adjectives)
• Simple grammars sentences (statements) follow a
  simple fixed pattern...
• http//www.dlib.org/dlib/october00/baker/10baker.h
  tml

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Basic Structures in Dublin Core Metadata

• The basic unit of metadata is a statement
• Statements consist of a property (a metadata
  element) and a value
• Metadata statements describe resources
• More about the Dublin Core Abstract model later

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What are the properties and values in the
following metadata statements?

• 245 00 a Amores perros h videorecording
• lttitlegt Nueve reinas lt/titlegt
• lttypegt MovingImage lt/typegt
• Different models for conveying related
  information
• Dublin Core syntax fits in more naturally with
  the structure of the Web

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implied verb
one of 15 properties
property value (an appropriate literal)
DCCreator DCTitle DCSubject DCDate...
implied subject
Resource
has
property
X
qualifiers (adjectives)
optional qualifier
optional qualifier
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The fifteen elements (properties)
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Varieties of qualifiersElement Refinements

• Make the meaning of an element narrower or more
  specific.
• a Date Created versus a Date Modified
• an IsReplacedBy Relation versus a Replaces
  Relation
• If your software does not understand the
  qualifier, you can safely ignore it.

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Varieties of QualifiersValue Encoding Schemes

• Says that the value is
• a term from a controlled vocabulary (e.g.,
  Library of Congress Subject Headings)
• a string formatted in a standard way (e.g.,
  "2001-05-02" means May 3, not February 5)
• Even if a scheme is not known by software, the
  value should be "appropriate" and usable for
  resource discovery.

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Resource
has
Subject
"Languages -- Grammar"
LCSH
Resource
has
Date
"2000-06-13"
Revised
ISO8601
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Dumb-Down Principle for Qualifiers

• Simple DC does not use element refinements or
  encoding schemes statements contain only value
  strings
• Qualified DC uses features of the DCMI Abstract
  Model, including element refinements and encoding
  schemes
• Dumbing-down is translating Qualified DC to
  simple DC
• Qualifiers refine meaning (but may be harder to
  understand)

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The One to One Principle

• Each resource should have one metadata
  description
• For example, do not describe a digital image of
  the Mona Lisa as if it were the original painting
• Group Related descriptions into description sets
• Describe an artist and his or her work
  separately, not in a single description

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Appropriate Values

• There are generally tradeoffs between local
  requirements and global requirements
• Use elements and qualifiers to meet the needs of
  your local context, but
• Keep in mind that machines and people use and
  interpret metadata, so
• Consider whether the values used will help
  discovery outside your local context

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Dublin Core as a multilingual metadata language

• Dublin Core has been translated into 20
  languages
• machine-readable tokens are shared by all
• human-readable labels are defined in different
  languages
• translations are distributed, maintained in many
  countries
• eventually linked in DCMI registry

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One token labels in many languages
dccreator
Server in Germany
DCMI Server
Server in Jakarta
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Metadata languages are "multilingual"

• Metadata is not a spoken language
• The words of metadata -- "elements" -- are
  symbols that stand for concepts expressible in
  multiple natural languages
• Standards may have dozens of translations
• Are concepts like "title", "author", or "subject"
  used the same way in English, Finnish, and Korean?

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DCMI Open Metadata Registry

• Managing vocabularies defined by the DCMI
• Languages
• Versioning
• Controlled vocabularies
• Foundation for modular, incremental integration
  and evolution
• The Registry working group is a Dublin Core
  Community with participants around the world

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The Dublin Core Abstract Model

• Terminology
• Simple versus Qualified DC
• Resources
• Descriptions
• Description sets
• Value Strings
• Element refinements
• Encoding Schemes
• Graphical representation of the Abstract Model
• Summary of general ideas

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Important DCMI Document concerningthe Abstract
Model and Syntax alternatives

• DCMI Abstract Model
• http//dublincore.org/documents/abstract-model
  /
• Expressing Dublin Core in HTML/XHTML meta and
  link elements
• http//dublincore.org/documents/dcq-html/
• Expressing Dublin Core metadata using the
  Resource Description Framework (RDF)
• http//dublincore.org/documents/dc-rdf/
• Expressing Dublin Core metadata using XML
• http//dublincore.org/documents/dc-xml/

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Simple versus Qualified DC

• Simple DC supports single descriptions using the
  15 base elements and value strings
• Qualified DC supports the richer features of the
  Abstract Model, and allows the use of all DCMI
  terms as well as other, non-DCMI terms.
• An application profile is used to specify a
  metadata application that includes DCMI terms in
  combination with non-DCMI terms (mix match
  metadata).

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The DCMI Abstract Model

• A data model for Dublin Core
• Agreed upon underlying structure for metadata
  statements
• Many years in the making -- long term contention
• Describes the structure of statements about
  resources that we make in our metadata language

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What is a resource?

• W3C definition
• anything that has identity electronic document,
  an image, a service
• not all resources are network retrievable e.g.
  human beings, corporations, and bound books can
  also be considered resources
• In other words, a resource is anything we can
  identify
• Physical things (books, people, airplanes.)
• Digital things (Images, web pages, services.)
• Concepts (colors, subjects, eras, places)
• In the DC context, the DCMI Type list describes
  the stuff we describe with DC metadata

43
Resource types for which DC is often used
DCMI TYPE Vocabulary
Collection Dataset Event
Image Interactive Resource Moving Image
Physical Object Service Software
Sound Still Image Text
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Abstract Model Descriptions

• A description is composed of
• One or more statements about a single resource
• Optionally, the URI of the resource being
  described
• Each statement is made up of
• A property URI (that identifies a property)
• A value URI (that identifies a value) and/or one
  or more representations of the value (a value
  string)

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Terminology Value Strings

• A value string is a human-readable string that
  represents the value of the property
• Each value string may have an associated value
  string language that is an ISO language tag
  (e.g., pt-BR)

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Terminology Element Refinements

• Elements are the same as properties
• Element refinements are the same as
  sub-properties
• An element refinement is a special case of an
  element that shares the meaning of its parent,
  but has narrower semantics
• Paulo is illustrator of a book, therefore he is
  also a contributor to the book
• Illustrator is an element refinement of
  contributor

47
Terminology Encoding Schemes

• Values and value strings can be qualified by
  encoding schemes in order to clarify their
  meaning
• A Vocabulary Encoding Scheme is used to indicate
  a terminology set from which a value is taken
• Stem cellsResearch is a value from LCSH
• 616.02774 is a value from DDC-22
• A syntax encoding scheme is used to indicate the
  structure of a value string
• 2004-10-12 is structured according to the
  
• W3CDTF rules for date encoding

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Terminology Description Sets

• The 11 principle dictates that each description
  describes one, and only one, resource
• We often need to describe grouped sets of
  descriptions, which are known in the abstract
  model as description sets
• An article and its authors
• A painting and its artist
• When description sets are exchanged between
  software applications, they are generally encoded
  according to a particular syntax in a metadata
  record

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Abstract Model summary (after Andy Powell)
Record (encoded as html, XML, or
RDF/XML
Description set
Resource Description (URI)
Resource Description (URI)
Resource Description (URI)
Statement

Statement

Vocabulary encoding scheme
Statement

value URI
property (URI)
language (pt-BR)
syntax encoding scheme
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General Ideas

• DC is not just the 15 elements, though they
  comprise the foundation for simple DC
• 50 properties (elements) have been approved by
  DCMI
• The model supports local declarations of
  additional properties
• The model supports application profiles (mixing
  DC elements with those of other sets)
• The model allows the grouping of descriptions to
  create more complex description entities

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Syntax Alternatives

• Choosing among alternatives
• HTML
• XML
• RDF/XML

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Syntax AlternativesHTML XML RDF/XML

• Three Web-based models for deploying metadata
• Each has advantages and disadvantages
• What is best depends on local constraints
• What is the objective of the system? How do
  these syntax alternatives support local
  functional requirements?
• Are there services and software to consume the
  metadata created?
• Are trained practitioners available to create and
  support the systems?

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Syntax Alternatives HTML

• Advantages
• Simple META tags embedded in content
• Widely deployed tools and knowledge
• Resource carries its metadata around with it
• Metadata is openly harvestable

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Syntax Alternatives HTML (continued)

• Disadvantages
• Limited structural richness (does not support
  hierarchical, tree-structured data
• Management of metadata is less reliable (the
  metadata is out in the wild)
• Describe one thing (the HTML document) and no
  more!

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Dublin Core in HTML (example)
ltheadgt ltlink rel"schema.DC" href"http//purl.org
/dc"gt ltmeta name"DC.title" contentDC
Metadata Tutorial ltmeta name"DC.creator"
contentStuart L. Weibel"gt ltmeta
name"DC.subject" xmllang en-US contentMeta
data"gt ltmeta name"DC.date" schemeDCTERMS.W3CDT
F" content2007-07-08"gt ltmeta
nameDCTERMS.audience content technical
librarianslt/headgt ltbodygt rest of html
document
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The namespaces for HTML encoding

• All DCMI terms (elements, element refinements,
  and encoding schemes) are found in
• DCMI Metadata Terms
• http//dublincore.org/documents/dcmi-terms/
• The namespaces are a result of historical
  developments
• DC original elements
• DCTERMS later elements

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Syntax Alternatives XML

• XML eXtensible Markup Language
• The standard for networked text and data
• Wide-spread tool support
• Parsers are widely available
• Extensibility (XML namespaces)
• Type definitions (XML Schema)
• Transformation and Rendering (XSLT)
• Rich linking semantics (XLINK)

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XML Schema

• Rich XML-based language for expressing data-type
  semantics
• Replaces arcane and limited DTD (origin in SGML)
• Facilities
• Data typing (both complex and primitive)
• Constraints (ranges, cardinality)
• Defaults (specify defaults for certain properties)

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Dublin Core fragment in XML
ltmetadata xmlnsdc"http//www.openarchives.org /
OAI/dc.xsd"gt   ltdccreatorgtCarl
Lagozelt/dccreatorgt ltdctitlegtAccommodating
Simplicity and Complexity in
Metadatalt/dctitlegt ltdcdategt2000-07-01lt/dcdat
egt       ltdcpublishergtCornell University,
Computer Sciencelt/dcpublishergt lt/metadatagt
Where is the rest of the stuff? In the
schema!   
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Case Study OAI-PMHOAI Protocol for Metadata
Harvesting

• Open Archives Initiative
• http//www.openarchives.org
• Simple Protocol for sharing metadata records
• Based on HTTP, XML, XML Schema, and XML
  namespaces
• Allows a harvester to query a remote repository
  for some or all of its metadata records
• DC is the default native metadata format in the
  OAI protocol

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Syntax Alternatives RDF

• RDF (Resource Description Format)
• Syntax expressed in XML
• W3C recommendation for encoding metadata (a
  semantic Web technology)
• Enabling technology for richly-structured
  metadata
• Rich data model (the DC Abstract Model is a
  constrained version of RDF)
• Metadata can be shared easily among independent
  applications that understand RDF
• W3C Resource Description Framework (RDF)
• http//www.w3.org/RDF/

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Summary Syntax alternatives

• Choices should be driven by local requirements
  and objectives
• Available expertise
• Costs of Deployment
• Objectives and functional requirements

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Association ModelsWhere do we keep the metadata?

• Embedded
• HTML META tags or XML or RDF-XML can be embedded
  in the resource, and hence travels with the
  resource
• Simple, but limited in structural richness
• Loosely coupled
• Shadow Files (like Adobes XMP Sidecar files)
• Requires a system to manage and insure that they
  stay in synch
• RDF or XML descriptions
• Third Party Metadata
• Stored in repositories such as library catalogs
• Easier to manage and maintain, and provide
  service
• Library catalogs, for example

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Questions about syntax alternatives?
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Application ProfilesMixing and Matching Metadata

• What is an Application Profile?
• Why bother?
• Creating new properties
• Documenting and declaring new
• properties
• Some examples

66
Application Profiles Mixing and Matching Metadata

• The mixing and matching of elements (properties)
  from separate metadata sets
• An expression of metadata modularity
• Implementers can benefit from peer applications
• Communities can harmonize their metadata, picking
  complementary properties
• Promotes convergence over time
• For application profiles to work, there must be
  public declarations of properties that conform to
  a common data model (or nearly so)

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Application Profile Definition

• Declaration of metadata properties used in a
  given organization or application or community
• Documentation of encodings, constraints, and
  creation guidelines
• Implies formal schemas (xml schemas or RDF
  schemas)
• Should promote both human understanding and
  machine interoperability
• The concept of application profiles applies to
  any metadata community of practice, not just DC
• DC has promoted their use and leads by example

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Why bother?

• One-size-fits-all metadata results in bloated,
  unmanageable specifications and applications
• APs allow tailoring a given metadata application
  to match the element set to specific functional
  requirements based on local or community needs,
  while retaining interoperability with a larger
  metadata community

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Creating an Application Profile

• Find out what others have done dont re-invent
  wheels!
• Develop community consensus
• Define Name, Label, definition relationships (see
  the DCMI Usage Board guidelines)
• Determine an appropriate URI (a home on the Web)
• Dublin Core Application Profile Guidelines
• http//dublincore.org/usage/documents/profile-
  guidelines/

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Document New Properties

• At very least a Web page with relevant
  information
• Better a web page with a public schema using new
  terms in an application profile
• Better still all properties available as part of
  a metadata registry

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Example Application Profiles

• DC-Library AP
• DC-Collection Description AP
• DC-Government AP
• DC-Education AP

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Some History of the Dublin CoreandHow the
Initiative Works

• The Beginnings
• Landmarks
• Workshops and Conference series
• What the initiative does
• Standardization
• Some example applications

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Dublin Core The Beginning

• A casual discussion at WWW-2 in Chicago, October
  of 1994
• How to make things on the Web easier to find?
• OCLC NCSA co-sponsored an invitational workshop
  in March of 1995
• The workshop became a workshop series, and
  eventually a conference series
• DCMI Dublin Core Metadata Initiative
• Governance and process evolved over time
• De facto standards maintenance body

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Dublin Core Landmarks

• 1994 Simple tags to describe Web pages
• 1995 The Dublin Core is one of many vocabularies
  needed ("Warwick Framework")
• 1996 The Dublin Core 13 elements expanded to 15
  - appropriate for Text and Images
• 1997 WF needs formal expression in a Resource
  Description Framework (RDF)

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Dublin Core Landmarks (continued)

• 2000 Dublin Core Metadata Initiative recommends
  qualifiers, broadens its organizational scope
  beyond the Core
• 2001 Workshop Series becomes a conference series
• DCMI Affiliates and a board of trustees
• 2005 Abstract Model (Finally)

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The Dublin Core Workshop Series

• Workshop Venues
• US DC 1, 3, 6
• UK DC 2
• Australia DC 4
• Finland DC 5
• Germany DC 7
• Canada DC 8
• Conferences
• Tokyo (2001) China (2004)
• Florence (2002) Spain (2005)
• Seattle (2003) Mexico (2006)

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DCMI Activities

• Standards development and maintenance
• Metadata registry and infrastructure
• Technical working groups and periodic workshops
• Tutorial materials and user guides
• Education and training
• Open source software
• Liaisons with other standards or user communities

79
Governance of DCMI

• DCMI has a Board of Trustees that oversees the
  operation and goals of the initiative
• Managing Director
• Makx Dekkers
• Director of Specifications and Documentation
• Tom Baker
• An Advisory Board of metadata experts provides
  guidance on metadata issues

80
The DCMI Usage Board

• The Usage Board is an editorial committee that
  evaluates proposals for new elements or revisions
• International selection of metadata experts
• Meet twice yearly
• Documents decisions and updates DCTERMS document

81
Affiliate Program

• DCMI has National Affiliates which support the
  Initiative and are represented on the Board of
  Trustees
• Finland
• UK
• Singapore
• New Zealand
• Korea
• OCLC has been the Host from the start

82
The Three Is

• Independent DCMI is not controlled by specific
  commercial or other interests and is not biased
  towards specific domains nor does it mandate
  specific technical solutions
• International DCMI encourages participation from
  organizations anywhere in the world, respecting
  linguistic and cultural differences
• Influenceable DCMI is an open organization
  aiming at building consensus among the
  participating organizations there are no
  prerequisites for participation

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The Work gets done by Communities and task
groups

• Accessibility Community
• Collection Description Community
• Education Community
• Environment Community
• Global Corporate Circle
• Government Community
• Kernel Community
• Libraries Community
• Localization and Internationalization Community
• Preservation Community
• Registry Community
• Social Tagging Community
• Standards Community
• Tools Community

84
Standardization of the Dublin Core

• IETF RFC 2413
• http//www.ietf.org/rfc/rfc2413.txt
• CEN Workshop Agreement (Europe)
• endorse Dublin Core elements as CWA13874
• NISO Z39.85
• National Information Standards Organization, an
  ANSI affiliate
• ISO 15836

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Metadata Applications - examples

• Governments
• 7 governments have adopted DC metadata
• Adobe products
• XMP Adobes variant of RDF
• Dublin Core is a base schema
• IPTC International Press and Telecommunications
  Council
• Dublin Core based standard for journalism
• Knowledge Management systems commonly use DC
  metadata
• Visual materials require metadata for findability
• Library Systems (mostly MARC cataloging, but
  increasingly other metadata as well)

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Metadata applications (continued)

• Search Systems
• Full text indexing is enormously useful
• Structured metadata improves search
• The Amazoogles are all aggressively courting
  metadata aggregators
• Cameras
• Automatically create metadata for each image
• Some even include GPS data
• Commerce systems require metadata
• Social Software applications are largely about
  enriching resource information with tags,
  reviews, and automated linking

87
To Sum Up

• Many purpose-built metadata standards
• Few have explicit data models
• Few interoperate
• Some will survive, others will not
• The Web demands convergence
• Break down silos between domains and communities
  of practice
• RDF should help promote convergence, but we are
  not there yet
• Expect more metadata standards, but hope for
  fewer

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How to Participate

• Join the
• DC-General
• mailing list
• Join a working
• group
• Information
• on lists and
• working groups
• is available at http//dublincore.org

89
Stuart L. Weibel
Visit me at http//weibel-lines.typepad.com Con
tact me at Weibel_at_oclc.org
Thank you for your attention