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

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


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

Dublin Core Metadata TutorialJuly 9,
2007Stuart WeibelSenior Research
ScientistOCLC Programs and Research
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
  • Acknowledgements I have borrowed liberally from
    tutorial slides sets from Tom Baker, Diane
    Hillman, Andy Powell, and Marty Kurth, available
    at Dublincore.org

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

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

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
  • Metadata is more useful in structured
    collections, used in combination with
    applications designed to take advantage of
    structured descriptions

Internet Commons includes Multiple Communities
Interoperabilityrequires conventions about
  • Semantics
  • The meaning of the elements
  • Structure
  • human-readable
  • machine-parseable
  • Syntax
  • grammars to convey semantics and structure

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

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

Metadata Takes Many Forms
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
  • focuses interoperability issues at package level
  • A conceptual framework, NOT an application

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.

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

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
  • 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

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

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

Dublin Core Starting Assumptions and Essential
  • 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

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

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
  • We are all "tourists" on the Internet.

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

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

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
  • Dublin Core syntax fits in more naturally with
    the structure of the Web

implied verb
one of 15 properties
property value (an appropriate literal)
DCCreator DCTitle DCSubject DCDate...
implied subject
qualifiers (adjectives)
optional qualifier
optional qualifier
The fifteen elements (properties)
Varieties of qualifiersElement Refinements
  • Make the meaning of an element narrower or more
  • a Date Created versus a Date Modified
  • an IsReplacedBy Relation versus a Replaces
  • If your software does not understand the
    qualifier, you can safely ignore it.

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.

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

The One to One Principle
  • Each resource should have one metadata
  • 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

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

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

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One token labels in many languages
Server in Germany
DCMI Server
Server in Jakarta
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?

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

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

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/

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

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

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
  • 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

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
Abstract Model Descriptions
  • A description is composed of
  • One or more statements about a single resource
  • Optionally, the URI of the resource being
  • 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

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)

Terminology Element Refinements
  • Elements are the same as properties
  • Element refinements are the same as
  • 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

Terminology Encoding Schemes
  • Values and value strings can be qualified by
    encoding schemes in order to clarify their
  • 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

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

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


Vocabulary encoding scheme

value URI
property (URI)
language (pt-BR)
syntax encoding scheme
General Ideas
  • DC is not just the 15 elements, though they
    comprise the foundation for simple DC
  • 50 properties (elements) have been approved by
  • 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

Syntax Alternatives
  • Choosing among alternatives
  • HTML
  • XML

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?

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

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

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
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
  • DC original elements
  • DCTERMS later elements

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)

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

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
Case Study OAI-PMHOAI Protocol for Metadata
  • Open Archives Initiative
  • http//www.openarchives.org
  • Simple Protocol for sharing metadata records
  • Based on HTTP, XML, XML Schema, and XML
  • 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

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
  • 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/

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

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
  • 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
  • Library catalogs, for example

Questions about syntax alternatives?
Application ProfilesMixing and Matching Metadata
  • What is an Application Profile?
  • Why bother?
  • Creating new properties
  • Documenting and declaring new
  • properties
  • Some examples

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)

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
  • 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

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

Creating an Application Profile
  • Find out what others have done dont re-invent
  • 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-

Document New Properties
  • At very least a Web page with relevant
  • 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

Example Application Profiles
  • DC-Library AP
  • DC-Collection Description AP
  • DC-Government AP
  • DC-Education AP

Some History of the Dublin CoreandHow the
Initiative Works
  • The Beginnings
  • Landmarks
  • Workshops and Conference series
  • What the initiative does
  • Standardization
  • Some example applications

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

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)

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)

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

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

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

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

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

The Work gets done by Communities and task
  • 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

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

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
  • Dublin Core based standard for journalism
  • Knowledge Management systems commonly use DC
  • Visual materials require metadata for findability
  • Library Systems (mostly MARC cataloging, but
    increasingly other metadata as well)

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

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

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

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