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An Introduction to the DCMI Abstract Model

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  1. An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  2. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  3. Context & Motivation: Why the DCAM? JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  4. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  5. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  6. The DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  7. Proposed Recommendation http://dublincore.org/documents/2007/04/02/abstract-model/

  8. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  9. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  10. DCAM Resource Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  11. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  12. DCAM Description Set Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  13. 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 • identifiesdescribed resource • one or more statements • a statement is made up of • exactly one property URI • identifiesproperty • exactly one value surrogate • a value surrogate is either a literal value surrogate or a non-literal value surrogate JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  14. Description Set Description Description Property URI Statement Statement Statement Literal Value Surrogate Property URI Non-Literal Value Surrogate Non-Literal Value Surrogate Property URI Resource URI Resource URI

  15. DCAM Description Set Model • a literal value surrogate is made up of • exactly one value string • encodesvalue • a non-literal value surrogate is made up of • zero or one value URIs • identifiesvalue • zero or one vocabulary encoding scheme URI • identifies a set of which the value is a member • zero or more value strings • representsvalue JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  16. Description Set Description Resource URI Description Property URI Statement Statement Literal Value Surrogate Statement Non-Literal Value Surrogate Property URI Value URI Vocab Enc Scheme URI Value string Value string Non-Literal Value Surrogate Resource URI Property URI Value URI Value string

  17. 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! JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  18. Description Set Description Resource URI Description Value URI Property URI Statement Statement Literal Value Surrogate Statement Non-Literal Value Surrogate Property URI Value URI Vocab Enc Scheme URI Value string Language Value string Non-Literal Value Surrogate Resource URI Property URI Value string Language Syntax Enc Scheme URI

  19. DCAM Description Set Model • a value may be described by another description JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  20. Description Set Description Resource URI Description Value URI Property URI Statement Statement Literal Value Surrogate Statement Non-Literal Value Surrogate Property URI Value URI Vocab Enc Scheme URI Value string Language Value string Syntax Enc Scheme URI Non-Literal Value Surrogate Resource URI Property URI Value string Language

  21. Description Set Description Resource URI Description Non-Literal Value Surrogate Property URI Statement Statement Literal Value Surrogate Statement Non-Literal Value Surrogate Property URI Value URI Vocab Enc Scheme URI Value string Language Value string Syntax Enc Scheme URI Property URI Value string Language

  22. Some example description sets JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  23. Description Set Statement Example 1: Single description containing one statement with non-literal value surrogate Description Resource URI Non-Literal Value Surrogate Property URI Value URI

  24. Example 1: Single description containing one statement with non-literal value surrogate Description Set Description <http://dublincore.org/documents/abstract-model/> Statement Non-Literal Value Surrogate <http://purl.org/dc/terms/publisher> Property URI Value URI <http://example.org/org/DCMI> @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> ) ) ) )

  25. Statement Value URI Vocab Enc Scheme URI Value string Value string 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

  26. Statement Example 2: Single description containing two statements with non-literal value surrogates Description Set Description <http://dublincore.org/documents/abstract-model/> Non-Literal Value Surrogate <http://purl.org/dc/terms/publisher> Property URI Value URI <http://example.org/org/DCMI> Statement Non-Literal Value Surrogate <http:/purl.org/dc/terms/subject> <http://example.org/org/mySH/h123> Value URI Property URI Vocab Enc Scheme URI <http://example.org/terms/mySH> “Metadata” en Value String "Métadonnées" fr Value String

  27. Example 2: Single description containing two statements with non-literal value surrogates @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 ("Métadonnées"Language (fr ) ) ) ) )

  28. Statement Statement 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

  29. Statement Statement Example 3: Two descriptions, statements with non-literal value surrogates & literal value surrogates Description Set Description <http://dublincore.org/documents/abstract-model/> Non-Literal Value Surrogate <http://purl.org/dc/terms/publisher> Property URI Value URI <http://example.org/org/DCMI> Statement Non-Literal Value Surrogate <http:/purl.org/dc/terms/subject> <http://example.org/org/mySH/h123> Value URI Property URI Vocab Enc Scheme URI <http://example.org/terms/mySH> “Metadata” en Value String "Métadonnées" fr Value String Description <http://example.org/org/DCMI> Literal Value Surrogate <http://xmlns.com/foaf/0.1/name> “Dublin Core Metadata Initiative” en Value String Property URI

  30. @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 ("Métadonnées"Language (fr ) ) ) ) Description ( ResourceURI ( <http://example.org/org/DCMI> ) Statement ( PropertyURI ( foaf:name ) LiteralValueString ( “Dublin Core Metadata Initiative” Language (en) ) ) ) )

  31. DCAM Vocabulary Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  32. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  33. 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 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  34. The DCAM & “DC application profiles” JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  35. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  36. The DCAM & “encoding guidelines” JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  37. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  38. System A System B Construct usingDCAM & DCAP Interpret usingDCAM DC DescriptionSet DC DescriptionSet Encode Decode DC-XMLInstance DC-XMLInstance <?xml version="1.0"?><dcx:descriptionSet>

  39. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  40. Some thoughts on Dublin Core in 2007 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  41. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  42. 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 JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

  43. An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester