An Introduction to the DCMI Abstract Model

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An Introduction to the DCMI Abstract Model

• JISC CETIS Metadata Digital Repositories SIG
  meeting, Manchester

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An Introduction to the DCMI Abstract Model

• Context Motivation Why the DCAM?
• The DCMI Abstract Model
• The DCAM DC application profiles
• The DCAM DCMI encoding guidelines
• Dublin Core in 2007

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Context Motivation Why the DCAM?
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Why DCAM? Context Motivation

• Some issues for DCMI c.2003
• Metadata vocabularies
• but what is a DC element?
• Encoding guidelines
• but what are we encoding?
• DC application profiles
• but what terms can we use?
• Simple and Qualified DC
• Grammatical Principles
• DC the Resource Description Framework

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Why DCAM? Context Motivation

• Work on DCAM from mid-2003, initiated by Andy
  Powell
• DCMI Recommendation, 2005-03-07
• Feedback from
• DCMI Usage Board
• DCMI working groups, designers of DCAPs
• Implementers of DCAPs
• Implementers of metadata registries
• Developers/implementers of related specs
• Semantic Web community
• Researchers
• Revision currently in progress
• Proposed Rec for Public Comment, 2007-02-05
• Proposed Rec for Public Comment, 2007-04-02

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The DCMI Abstract Model
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Proposed Recommendation http//dublincore.org/docu
ments/2007/04/02/abstract-model/
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The DCMI Abstract Model

• DCAM concerned with description of resources
• DCAM adopts Web Architecture/RFC3986 definition
  of resource
• the term "resource" is used in a general sense
  for whatever might be identified by a URI.
  Familiar examples include an electronic document,
  an image, a source of information with consistent
  purpose (e.g., "today's weather report for Los
  Angeles"), a service (e.g., an HTTP to SMS
  gateway), a collection of other resources, and so
  on.
• A resource is not necessarily accessible via the
  Internet e.g., human beings, corporations, and
  bound books in a library can also be resources.
• Likewise, abstract concepts can be resources,
  such as the operators and operands of a
  mathematical equation, the types of a
  relationship (e.g., "parent" or "employee"), or
  numeric values (e.g., zero, one, and infinity).
• RFC3986 URI Syntax

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The DCMI Abstract Model

• DCAM describes
• Components and constructs that make up an
  information structure (DC description set)
• How that information structure is to be
  interpreted
• DCAM does not describe how to represent DC
  description set in concrete form
• DCAM describes various types of metadata term,
  but does not specify the use of any fixed set of
  terms
• Made up of three related information models
• Resource model
• Description set model
• Vocabulary model

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DCAM Resource Model
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DCAM Resource Model

• The view of the world on which DC metadata is
  based
• a described resource is described using one or
  more property-value pairs
• a property-value pair is made up of
• exactly one property and
• exactly one value
• a value is a resource
• a value is either a literal value or a
  non-literal value
• i.e. similar to RDF model of binary relations
  between resources entity-relational model

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DCAM Description Set Model
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DCAM Description Set Model

• The structure of DC metadata
• Uses URIs to refer to resources metadata terms
  (like RDF)
• a description set is made up of one or more
  descriptions, each of which describes one
  resource
• a description is made up of
• zero or one described resource URI
• identifies described resource
• one or more statements
• a statement is made up of
• exactly one property URI
• identifies property
• exactly one value surrogate
• a value surrogate is either a literal value
  surrogate or a non-literal value surrogate

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Resource URI
Resource URI
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DCAM Description Set Model

• a literal value surrogate is made up of
• exactly one value string
• encodes value
• a non-literal value surrogate is made up of
• zero or one value URIs
• identifies value
• zero or one vocabulary encoding scheme URI
• identifies a set of which the value is a member
• zero or more value strings
• represents value

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Value URI
Value string
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DCAM Description Set Model

• a value string is either a plain value string or
  a typed value string
• a plain value string may have an associated value
  string language
• a typed value string is associated with a syntax
  encoding scheme URI
• Not going to say more about SES today!

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Syntax Enc Scheme URI
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DCAM Description Set Model

• a value may be described by another description

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Some example description sets
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Example 1 Single description containing one
statement with non-literal value surrogate
Description
Resource URI
Non-Literal Value Surrogate
Property URI
Value URI
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Example 1 Single description containing one
statement with non-literal value surrogate
Description Set
Description
lthttp//dublincore.org/documents/abstract-model/gt
Statement
Non-Literal Value Surrogate
lthttp//purl.org/dc/terms/publishergt
Property URI
Value URI
lthttp//example.org/org/DCMIgt
_at_prefix dcterms lthttp//purl.org/dc/terms/gt
. DescriptionSet ( Description (
ResourceURI ( lthttp//dublincore.org/documents/abs
tract-model/gt ) Statement (
PropertyURI ( dctermspublisher )
ValueURI (lthttp//example.org/org/DCMIgt )
) ) )
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Example 2 Single description containing two
statements with non-literal value surrogates
Description Set
Description
Resource URI
Non-Literal Value Surrogate
Property URI
Value URI
Statement
Non-Literal Value Surrogate
Property URI
Language
Language
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Example 2 Single description containing two
statements with non-literal value surrogates
Description Set
Description
lthttp//dublincore.org/documents/abstract-model/gt
Non-Literal Value Surrogate
lthttp//purl.org/dc/terms/publishergt
Property URI
Value URI
lthttp//example.org/org/DCMIgt
Statement
Non-Literal Value Surrogate
lthttp/purl.org/dc/terms/subjectgt
lthttp//example.org/org/mySH/h123gt
Value URI
Property URI
Vocab Enc Scheme URI
lthttp//example.org/terms/mySHgt
Metadata
en
Value String
"Métadonnées"
fr
Value String
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Example 2 Single description containing two
statements with non-literal value surrogates
_at_prefix dcterms lthttp//purl.org/dc/terms/gt
. DescriptionSet ( Description (
ResourceURI ( lthttp//dublincore.org/documents/abs
tract-model/gt ) Statement (
PropertyURI ( dctermspublisher )
ValueURI (lthttp//example.org/org/DCMIgt )
) Statement ( PropertyURI (
dctermssubject ) ValueURI
(lthttp//example.org/mySH/h123gt )
VocabEncSchemeURI (lthttp//example.org/terms/mySHgt
) ValueString ( Metadata Language (en
) ) ValueString ("Métadonnées" Language
(fr ) ) ) ) )
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Example 3 Two descriptions, statements with
non-literal value surrogates literal value
surrogates
Description Set
Description
Resource URI
Non-Literal Value Surrogate
Property URI
Value URI
Statement
Non-Literal Value Surrogate
Property URI
Value URI
Vocab Enc Scheme URI
Value string
Language
Value string
Language
Description
Resource URI
Literal Value Surrogate
Property URI
Value string
Language
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Example 3 Two descriptions, statements with
non-literal value surrogates literal value
surrogates
Description Set
Description
lthttp//dublincore.org/documents/abstract-model/gt
Non-Literal Value Surrogate
lthttp//purl.org/dc/terms/publishergt
Property URI
Value URI
lthttp//example.org/org/DCMIgt
Statement
Non-Literal Value Surrogate
lthttp/purl.org/dc/terms/subjectgt
lthttp//example.org/org/mySH/h123gt
Value URI
Property URI
Vocab Enc Scheme URI
lthttp//example.org/terms/mySHgt
Metadata
en
Value String
"Métadonnées"
fr
Value String
Description
lthttp//example.org/org/DCMIgt
Literal Value Surrogate
lthttp//xmlns.com/foaf/0.1/namegt
Dublin Core Metadata Initiative
en
Value String
Property URI
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_at_prefix dcterms lthttp//purl.org/dc/terms/gt
. _at_prefix foaf lthttp//xmlns.com/foaf/0.1/gt
. DescriptionSet ( Description (
ResourceURI ( lthttp//dublincore.org/documents/abs
tract-model/gt ) Statement (
PropertyURI ( dctermspublisher )
ValueURI (lthttp//example.org/org/DCMIgt )
) Statement ( PropertyURI (
dctermssubject ) ValueURI
(lthttp//example.org/mySH/h123gt )
VocabEncSchemeURI (lthttp//example.org/terms/mySHgt
) ValueString ( Metadata Language (en
) ) ValueString ("Métadonnées" Language
(fr ) ) ) ) Description (
ResourceURI ( lthttp//example.org/org/DCMIgt )
Statement ( PropertyURI ( foafname )
LiteralValueString ( Dublin Core
Metadata Initiative Language (en) ) )
) )
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DCAM Vocabulary Model
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DCAM Vocabulary Model

• a vocabulary is a set of terms (property, class,
  vocabulary encoding scheme, syntax encoding
  scheme)
• a resource may be an instance of one or more
  classes
• a resource may be a member of one or more
  vocabulary encoding schemes
• a property may have a range relationship with one
  or more classes
• a property may have a domain relationship with
  one or more classes
• a property may have a subproperty relationship
  with one or more properties
• a class may have a subclass relationship with one
  or more classes
• RDF Schema

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Current/recent issues

• DCAM RDF
• Mapping to RDF graphs specified by Expressing DC
  metadata using RDFhttp//dublincore.org/documents
  /2007/04/02/dc-rdf
• Clarifying distinction between things
  strings
• DCAM as abstract syntax for RDF v DCAM as domain
  (metadata) model
• Reflects DCMI communitys view of metadata
• Uses concepts developed by that community
• Formulated so as to be compatible with RDF/RDFS
• Possibly require further note(s) on merging,
  inferencing

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The DCAM DC application profiles
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The DCAM DC application profiles

• DCAM does not specify the set of terms referenced
  in a description set
• Notion of DC application profile widely used
  within DCMI and by DC implementers
• Typically annotated lists of terms used in DC
  metadata so as to meet some domain/community
  requirements
• Terms defined by DCMI or by other agencies
• Currently DCMI has no formal model for DCAP
• DCAP as description set profile
• Specification of how to construct description
  sets to meet some set of requirements
• Definition of DCAP based on
• functional requirements
• domain model

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The DCAM encoding guidelines
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The DCAM encoding guidelines

• DCAM is independent of any concrete syntax
• For transfer between applications, descriptions
  must be encoded as digital objects (records)
• DCMI Encoding Guidelines describe
• how description set is serialised/encoded as a
  record using a format
• how records conforming to format are
  decoded/interpreted as description sets

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The DCAM encoding guidelines

• Current DCMI Encoding Guidelines specs
• Pre-date development of DCAM
• Use earlier, simpler DC abstract models
• Not fully compatible with DCAM description set
  model
• Currently, no DCMI recommendation for
  machine-readable format for description set model
• Updating of specs in progress (2007)
• DC-XML
• DC in X/HTML link/meta elements
• Meanwhile, some formats defined outside of DCMI
• e.g. Eprints DC-XML

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Some thoughts on Dublin Core in 2007
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Dublin Core in 2007

• Not just a set of 15 elements
• Not even a set of 15 elements, 70-odd other
  terms (element refinements, vocabulary encoding
  schemes, syntax encoding schemes, classes)
• Not just Simple Dublin Core and Qualified
  Dublin Core
• Not limited to simple flat atomic
  descriptions

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Dublin Core in 2007

• a framework (the DCAM)
• which describes how to use certain types of terms
• ... to make statements...
• ... that form descriptions (of resources)
• that can be grouped together as description
  sets
• a set of specifications for encoding description
  sets using various formats
• a managed vocabulary of widely useful terms
• which can be referenced in statements
• support for defining additional vocabularies of
  terms
• which can be referenced in statements
• support for defining DC application profiles
• which describe how to construct description sets
  for some particular set of requirements
• extensibility, modularity, compatibility with
  Semantic Web

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An Introduction to the DCMI Abstract Model

• JISC CETIS Metadata Digital Repositories SIG
  meeting, Manchester