Metadata Modularization Concepts and Tools

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Metadata ModularizationConcepts and Tools

• Carl Lagoze
• CS502
• 2001-03-14

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Metadata
Structured data about data.
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Why is Metadata important?

• Key to organizing, managing, preserving, and
  locating content and services in digital libraries

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Why is Metadata difficult?

• Cost
• Interoperability
• Syntax
• Semantics
• Customizability
• Extensibility

• Distribution
• Integrity, Authenticity, Quality
• Human and Machine Factors
• Naming

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Metadata Thoughts

• Metadata takes a variety of forms
• descriptive cataloging
• specialized
• terms and conditions
• administrative
• content ratings
• provenance
• linkage

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More Metadata Thoughts

• New metadata sets will continually evolve
• Many metadata sets are community-specific
• administration
• use
• Human and machine use

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Dublin Core

• Metadata Set for Simple Resource Discovery
• 15 elements allowing simple descriptive sentences
  about document like objects
• Document has title Hamlet
• Document has creator William Shakespeare
• Document has subject love and anguish

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The Dublin Core 15

• Title
• Creator
• Subject /Keywords
• Description
• Publisher
• Other Contributor
• Date

• Resource Type
• Format
• Resource Identifier
• Source
• Language
• Relation
• Coverage
• Rights Management

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A Scope for the Dublin Core

• Increase or decrease number of elements?
• Structured or Unstructured value syntax?
• Accommodate community extensions?

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Warwick Framework

• Provide context for Dublin Core effort
• Integrate multiple sets of metadata addressing
  issues of
• individual integrity
• distinct audiences
• separate realms of responsibility and management

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Warwick Framework Design

• Containers for aggregating
• Packages of typed metadata sets
• General principles - information hiding
• only operation defined at container level returns
  sequence of contained packages
• packages are opaque at the container level
• access to package contents subject to terms and
  conditions

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Package Types

• Simple metadata set
• segregating distinct metadata into separate
  packages
• Recursive container
• nesting semantically related metadata sets
• Indirect reference
• allowing distribution and sharing of metadata sets

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Metadata Container
Container

Package Dublin Core
Package MARC record
Package Indirect Reference
Package Terms and Conditions
URI
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Open Implementation Issues

• Data encoding
• Semantic interaction of overlapping sets
• between semantically-related packages
• between semantically distinct packages
• Type registry

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Modeling Encoding Metadata Components XML
Namespaces

• Prevent term clash
• record?, creator?
• Establish concept spaces through URIs

xmlnsdchttp//purl.org/dcxmlnsabchttp//ilr
t.ac.uk/abcltdccreatorgtHerbert Van de
Sompellt/dccreatorgtltabcorganizationgtCornell
Universitylt/abcorganizationgt
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Modeling Encoding Metadata Components RDF

• RDF (Resource Description Format)
• The instantiation of the Warwick Framework on the
  Web
• Provides enabling technology for
  richly-structured metadata
• Rich data model supporting notions of distinct
  entities and properties
• Syntax expressed in XML

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RDF Components

• Formal data model
• Syntax for interchange of data
• Schema Type system (schema model)

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RDF Data Model

• Directed labeled graphs
• Model elements
• Resource
• Property
• Value
• Statement
• Containers

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RDF Model Primitives
Resource
Property
Value
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RDF Syntax Example
URIR
Title
CIMI Presentation
Creator
Eric Miller
ltRDF xmlns http//www.w3.org/TR/WD-rdf-syntax
xmlnsdc http//purl.org/dc/element
s/1.0/gt ltDescription about URIRgt
ltdcTitlegt CIMI Presentation lt/dcTitlegt
ltdcCreatorgt Eric Miller lt/dcCreatorgt
lt/Descriptiongt lt/RDFgt
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RDF Model Example 2
URIR
Title
CIMI Presentation
Creator
Eric Miller
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RDF Syntax Example 2
ltRDF xmlns http//www.w3.org/TR/WD-rdf-syntax
xmlnsdc http//purl.org/dc/element
s/1.0/ xmlnsbib http//www.bib.org
/personsgt ltDescription about URIRgt
ltdcTitlegt CIMI Presentation lt/dcTitlegt
ltoaCreatorgt ltDescriptiongt
ltbibNamegt Eric Miller lt/bibNamegt
ltbibEmailgt emiller_at_oclc.org lt/bibEmailgt
ltbibAff resource http//www.oclc.org /gt
lt/Descriptiongt lt/oaCreatorgt
lt/Descriptiongt lt/RDFgt
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RDF Containers

• Permit the aggregation of several values for a
  property
• Express multiple aggregation semantics
• unordered
• sequential or priority order
• alternative

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RDF Schemas

• Declaration of vocabularies
• properties defined by a particular community
• characteristics of properties and/or constraints
  on corresponding values
• Schema Type System - Basic Types
• Property, Class, SubClassOf, Domain, Range
• Minimal (but extensible) at this time
• minimize significant clashes with typing system
  designed for XML Schema WG
• Expressible in the RDF model and syntax

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Relationships among vocabularies
dcCreator
marc100
msdirector
bibAuthor
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Bringing it together

• RDF Data Model
• Support consistent encoding, exchange and
  processing of metadata critical when aggregating
  data from multiple sources
• RDF Schema
• Declare, define, reuse vocabularies
• RDF Metadata transmission
• XML encoding

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Interoperability among Metadata Vocabularies
- projections to application-specific metadata
vocabularies
core classes
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Attribute/Value approaches to metadata
The playwright of Hamlet was Shakespeare
Hamlet has a creator
Shakespeare
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run into problems for richer descriptions
The playwright of Hamlet was Shakespeare,who was
born in Stratford
Hamlet has a creator
Shakespeare
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because of their failure to model entity
distinctions
Shakespeare
name
R1
R2
creator
birthplace
title
Stratford
Hamlet
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Understanding Metadata based on Query Capabilities

• Simple boolean tags?
• Agent, time, place questions?
• Who was responsible for what and when

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Applying a Model-Centric Approach

• Formally define common entities and relationships
  underlying multiple metadata vocabularies
• Describe them (and their inter-relationships) in
  a simple logical model
• Provide the framework for extending these common
  semantics to domain and application-specific
  metadata vocabularies.

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Conceptual BasisEvolution of Content over Time
IFLA Entity Model
From Bearman, et. al., D-Lib Magazine, January
1999.
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Events are key to understanding metadata
relationships?

• Recognizing inherent lifecycle aspects of digital
  content - transformation of input resources to
  output resources and of their descriptions.
  (e.g., IFLA model)
• Modeling implied events as first-class objects
  provides attachment points for common entities
  e.g., agents, contexts (times places), roles.
• Clarifying attachment points facilitates mapping
  across common entities in different vocabularies.

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Content, Events, Descriptions
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Museum Data