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An Introduction to the DCMI Abstract Model
 

An Introduction to the DCMI Abstract Model

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Describes the 2007-04-02 version of the DCMI Abstract Model and presents some thoughts on the way the emergence of the DCAM has the potential to change perceptions of "Dublin Core".

Describes the 2007-04-02 version of the DCMI Abstract Model and presents some thoughts on the way the emergence of the DCAM has the potential to change perceptions of "Dublin Core".

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An Introduction to the DCMI Abstract Model An Introduction to the DCMI Abstract Model Presentation Transcript

  • An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester
  • 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
  • Context & Motivation: Why the DCAM?
  • 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
  • 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
  • The DCMI Abstract Model
  • Proposed Recommendation http://dublincore.org/documents/2007/04/02/abstract-model/
  • 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
  • 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
  • DCAM Resource Model
  • 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
  • DCAM Description Set Model
  • 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
  • Resource URI Resource URI Description Set Description Statement Property URI Literal Value Surrogate Description Statement Property URI Non-Literal Value Surrogate Statement Property URI Non-Literal Value Surrogate
  • 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
  • Value URI Value string Description Set Description Statement Property URI Resource URI Literal Value Surrogate Description Statement Property URI Resource URI Non-Literal Value Surrogate Statement Property URI Non-Literal Value Surrogate Vocab Enc Scheme URI Value URI Value string Value string
  • 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!
  • Syntax Enc Scheme URI Description Set Description Statement Property URI Resource URI Literal Value Surrogate Description Statement Property URI Resource URI Non-Literal Value Surrogate Statement Property URI Non-Literal Value Surrogate Value URI Vocab Enc Scheme URI Value URI Value string Value string Value string Language Language
  • DCAM Description Set Model
    • a value may be described by another description
  • Description Set Description Statement Property URI Resource URI Literal Value Surrogate Description Statement Property URI Resource URI Non-Literal Value Surrogate Statement Property URI Non-Literal Value Surrogate Value URI Vocab Enc Scheme URI Value URI Value string Value string Value string Syntax Enc Scheme URI Language Language
  • Description Set Description Statement Property URI Literal Value Surrogate Description Statement Property URI Resource URI Non-Literal Value Surrogate Statement Property URI Non-Literal Value Surrogate Vocab Enc Scheme URI Value URI Value string Value string Value string Syntax Enc Scheme URI Language Language
  • Some example description sets
  • Description Property URI Resource URI Example 1: Single description containing one statement with non-literal value surrogate Non-Literal Value Surrogate Value URI Description Set Statement
  • Description Set Description Statement <http://purl.org/dc/terms/publisher> <http://dublincore.org/documents/abstract-model/> <http://example.org/org/DCMI> Example 1: Single description containing one statement with non-literal value surrogate @prefix dcterms <http://purl.org/dc/terms/> . DescriptionSet ( Description ( ResourceURI ( <http://dublincore.org/documents/abstract-model/> ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI (<http://example.org/org/DCMI> ) ) ) ) Non-Literal Value Surrogate Property URI Value URI
  • Description Set Description Property URI Resource URI Example 2: Single description containing two statements with non-literal value surrogates Statement Property URI Non-Literal Value Surrogate Non-Literal Value Surrogate Value URI Language Language Statement Vocab Enc Scheme URI Value URI Value string Value string
  • Description Set Description Example 2: Single description containing two statements with non-literal value surrogates Statement <http:/purl.org/dc/terms/subject> Non-Literal Value Surrogate Non-Literal Value Surrogate <http://example.org/terms/mySH> “ Metadata” &quot;Métadonnées&quot; en fr <http://purl.org/dc/terms/publisher> <http://dublincore.org/documents/abstract-model/> <http://example.org/org/DCMI> Property URI Value URI <http://example.org/org/mySH/h123> Value URI Property URI Vocab Enc Scheme URI Value String Value String Statement
  • @prefix dcterms <http://purl.org/dc/terms/> . DescriptionSet ( Description ( ResourceURI ( <http://dublincore.org/documents/abstract-model/> ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI (<http://example.org/org/DCMI> ) ) Statement ( PropertyURI ( dcterms:subject ) ValueURI (<http://example.org/mySH/h123> ) VocabEncSchemeURI (<http://example.org/terms/mySH> ) ValueString ( “Metadata” Language (en ) ) ValueString ( &quot;Métadonnées&quot; Language (fr ) ) ) ) ) Example 2: Single description containing two statements with non-literal value surrogates
  • Description Set Description Property URI Resource URI Example 3: Two descriptions, statements with non-literal value surrogates & literal value surrogates Statement Property URI Non-Literal Value Surrogate Non-Literal Value Surrogate Vocab Enc Scheme URI Value URI Value string Value string Value URI Language Language Description Resource URI Property URI Literal Value Surrogate Value string Language Statement Statement
  • Description Set Description Statement <http:/purl.org/dc/terms/subject> Non-Literal Value Surrogate Non-Literal Value Surrogate <http://example.org/terms/mySH> “ Metadata” &quot;Métadonnées&quot; en fr <http://purl.org/dc/terms/publisher> <http://dublincore.org/documents/abstract-model/> <http://example.org/org/DCMI> Property URI Value URI <http://example.org/org/mySH/h123> Value URI Property URI Vocab Enc Scheme URI Value String Value String Example 3: Two descriptions, statements with non-literal value surrogates & literal value surrogates Description <http://example.org/org/DCMI> <http://xmlns.com/foaf/ 0.1/name> Literal Value Surrogate “ Dublin Core Metadata Initiative” en Value String Property URI Statement Statement
  • @prefix dcterms <http://purl.org/dc/terms/> . @prefix foaf <http://xmlns.com/foaf/0.1/> . DescriptionSet ( Description ( ResourceURI ( <http://dublincore.org/documents/abstract-model/> ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI (<http://example.org/org/DCMI> ) ) Statement ( PropertyURI ( dcterms:subject ) ValueURI (<http://example.org/mySH/h123> ) VocabEncSchemeURI (<http://example.org/terms/mySH> ) ValueString ( “Metadata” Language (en ) ) ValueString ( &quot;Métadonnées&quot; Language (fr ) ) ) ) Description ( ResourceURI ( <http://example.org/org/DCMI> ) Statement ( PropertyURI ( foaf:name ) LiteralValueString ( “Dublin Core Metadata Initiative” Language (en) ) ) ) )
  • DCAM Vocabulary Model
  • 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
  • Current/recent issues
    • DCAM & RDF
      • Mapping to RDF graphs specified by Expressing DC metadata using RDF http://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 community’s 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
  • The DCAM & “DC application profiles”
  • 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
  • The DCAM & “encoding guidelines”
  • 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
  • System A DC Description Set DC-XML Instance Encode Construct using DCAM & DCAP Decode DC Description Set Interpret using DCAM System B DC-XML Instance <?xml version=&quot;1.0&quot;?> <dcx:descriptionSet>
  • 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
  • Some thoughts on Dublin Core in 2007
  • 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
  • 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
  • An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester