1. Pete Johnston, Eduserv Foundation pete.johnston@eduserv.org.uk www.eduserv.org.uk/foundation 16 April 2007 An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester

2. 16 April 2007JISC 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

3. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 3 Context & Motivation: Why the DCAM?

4. 16 April 2007JISC 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

5. 16 April 2007JISC 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

6. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 6 The DCMI Abstract Model

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

8. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 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

9. 16 April 2007JISC 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

10. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 10 DCAM Resource Model

11. 16 April 2007JISC 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

12. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 12 DCAM Description Set Model

13. 16 April 2007JISC 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 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

14. 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

15. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 15 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

16. 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

17. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 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!

18. 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 Syntax Enc Scheme URI Language

19. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 19 DCAM Description Set Model a value may be described by another description

20. 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 Syntax Enc Scheme URI Language

21. 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 Syntax Enc Scheme URI Language

22. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 22 Some example description sets

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

24. Description Set Description Statement Example 1: Single description containing one statement with non-literal value surrogate @prefix dcterms. DescriptionSet ( Description ( ResourceURI ( ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI ( ) ) Non-Literal Value Surrogate Property URIValue URI

25. Description Set Description Statement Property URI Resource URI Example 2: Single description containing two statements with non-literal value surrogates Statement Property URI Non-Literal Value Surrogate Vocab Enc Scheme URI Value URI Value string Value URI Language

26. Description Set Description Statement Example 2: Single description containing two statements with non-literal value surrogates Statement Non-Literal Value Surrogate “Metadata” "Métadonnées" en fr Property URIValue URI Value URI Property URI Vocab Enc Scheme URI Value String

27. @prefix dcterms. DescriptionSet ( Description ( ResourceURI ( ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI ( ) ) Statement ( PropertyURI ( dcterms:subject ) ValueURI ( ) VocabEncSchemeURI ( ) ValueString ( “Metadata” Language (en ) ) ValueString ("Métadonnées" Language (fr ) ) ) Example 2: Single description containing two statements with non-literal value surrogates

28. Description Set Description Statement Property URI Resource URI Example 3: Two descriptions, statements with non-literal value surrogates & literal value surrogates Statement Property URI Non-Literal Value Surrogate Vocab Enc Scheme URI Value URI Value string Value URI Language Description Resource URI Statement Property URI Literal Value Surrogate Value stringLanguage

29. Description Set Description Statement Non-Literal Value Surrogate “Metadata” "Métadonnées" en fr Property URIValue URI Value URI Property URI Vocab Enc Scheme URI Value String Example 3: Two descriptions, statements with non-literal value surrogates & literal value surrogates Description Statement Literal Value Surrogate “Dublin Core Metadata Initiative”en Value String Property URI

30. @prefix dcterms. @prefix foaf. DescriptionSet ( Description ( ResourceURI ( ) Statement ( PropertyURI ( dcterms:publisher ) ValueURI ( ) ) Statement ( PropertyURI ( dcterms:subject ) ValueURI ( ) VocabEncSchemeURI ( ) ValueString ( “Metadata” Language (en ) ) ValueString ("Métadonnées" Language (fr ) ) ) Description ( ResourceURI ( ) Statement ( PropertyURI ( foaf:name ) LiteralValueString ( “Dublin Core Metadata Initiative” Language (en) ) )

31. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 31 DCAM Vocabulary Model

32. 16 April 2007JISC 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

33. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 33 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 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

34. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 34 The DCAM & “DC application profiles”

35. 16 April 2007JISC 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

36. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 36 The DCAM & “encoding guidelines”

37. 16 April 2007JISC 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

38. 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

39. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 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

40. 16 April 2007JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester 40 Some thoughts on Dublin Core in 2007

41. 16 April 2007JISC 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

42. 16 April 2007JISC 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

43. Pete Johnston, Eduserv Foundation pete.johnston@eduserv.org.uk www.eduserv.org.uk/foundation 16 April 2007 An Introduction to the DCMI Abstract Model JISC CETIS Metadata & Digital Repositories SIG meeting, Manchester