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An Introduction to Dublin Core

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1 An Introduction to Dublin Core
Making Sense of Metadata, Society of Archivists EAD/Data Exchange SIG London, Thursday 17 November 2005 Pete Johnston Research Officer, UKOLN, University of Bath UKOLN is supported by:

2 An Introduction to Dublin Core
A brief history What is Dublin Core, really? The DCMI Abstract Model Encoding Dublin Core metadata DC Application Profiles DC in practice

3 A Brief History

4 A brief history (1) Mid 1990s: rapid growth of World Wide Web
Challenge of resource discovery search engines providing many hits, but little precision recognition that library approach to cataloguing could not scale to Web resources 1995 OCLC/NCSA Workshop in Dublin, Ohio interdisciplinary consensus on 13 "metadata elements" for discovery of "document-like objects" relatively simple, usable by non-cataloguers 1996 OCLC/CNI Workshop in Dublin, Ohio expand to 15 elements explicitly cross-domain for discovery of broad range of "resources"

5 The Dublin Core Metadata Element Set
Title Subject Description Creator Publisher Contributor Date Type Format Identifier Source Language Relation Coverage Rights

6 A brief history (2) 1997-2000 Development of notion of "qualification"
tension between simplicity and complexity element refinement Narrow the meaning of a DC element e.g. "date modified" v "date" encoding scheme Provide additional information about a value e.g. that a subject is a Library of Congress Subject Heading the "Dumb-Down" principle Rules for transforming "qualified" description into "simple" description the "One-to-One" rule A DC description describes exactly one resource

7 A brief history (3) 1997-2000 What is a "resource"?
e.g. Can the DCMES be applied to people? DCMI Type Vocabulary Collection, Dataset, Event, Image (Still or Moving), Interactive Resource, Service, Software, Sound, Text, Physical Object But still fairly non-prescriptive 1998- Emergence of Resource Description Framework (RDF) "Grammatical Principles" as informal data model

8 A brief history (4) Development of notion of DC "Application Profile" tailoring metadata standards for context providing local guidelines, constraints combining components from different sources Formalisation of DCMI Abstract Model concepts used in DC metadata different types of terms used in DC metadata how those terms used in combination to construct descriptions

9 What is Dublin Core, really?

10 Dublin Core is... a conceptual framework/set of rules...
DCMI Abstract Model describes how to use certain types of terms ... to make statements... ... that form descriptions (of resources) a "core" vocabulary/set of terms... managed by DCMI (Usage Board) growing (relatively) slowly as new requirements arise each identified by a Uniform Resource Identifier (URI) a set of specifications for representing or encoding DC metadata descriptions in various formats

11 DCMI Abstract Model (a slightly simplified view)

12 DCMI Abstract Model A description describes exactly one resource
may specify a resource URI consists of a set of statements

13 DCMI Abstract Model: Descriptions
Resource URI Statement

14 DCMI Abstract Model A statement must contain a reference to a property
property URI all DC "elements" are properties properties may be defined by agencies other than DCMI a reference to a second resource (value) value URI, and/or one or more value representations value string rich representation

15 DCMI Abstract Model: Statements
Description Resource URI Property URI Value URI Value string Rich representation Statement

16 DCMI Abstract Model A statement may contain
a reference to a vocabulary encoding scheme vocabulary encoding scheme URI type of value a reference to a syntax encoding scheme syntax encoding scheme URI how value string is interpreted

17 DCMI Abstract Model: Statements
Description Resource URI Property URI Rich representation Value URI Vocab Enc Scheme URI Value string Syntax Enc Scheme URI Statement

18 DCMI Abstract Model A description describes one resource
Applications typically based on description sets groups of descriptions where the described resources may be related in some way Description sets encoded or serialised as records according to rules of binding

19 Description Set Description Resource URI Property URI Rich representation Value URI Vocab Enc Scheme URI Value string Syntax Enc Scheme URI Statement Resource URI Property URI Rich representation Value URI Vocab Enc Scheme URI Value string Syntax Enc Scheme URI

20 Encoding Dublin Core metadata (a very brief introduction!)
For full details see the DCMI recommendations and Andy Powell's tutorial

21 DCMI Abstract Model and Bindings
For transfer between applications, descriptions must be represented as digital objects Binding maps between constructs in conceptual model and components in a digital format Two way encoding application: description set -> record decoding application: record -> description set DCMI currently provides three "encoding guidelines" specifications Other agencies may also provide bindings

22 Using X/HTML meta & link elements
The set of meta/link elements represent a single DC description. The resource described is the X/HTML document in which the metadata is embedded. Each meta/link element represents a single statement Property and Encoding Scheme URIs encoded as prefixed names <link rel="schema.DC" href="http://purl.org/dc/elements/1.1/" /> <link rel="schema.DCTERMS" href="http://purl.org/dc/terms/" /> <meta name="DC.title" content="A guide to DC metadata" /> <meta name="DCTERMS.audience" content="information managers" /> <meta name="DC.language" scheme="DCTERMS.ISO639-2" content="eng" /> <link rel="DCTERMS.references" href="http://dublincore.org/documents/dcq-html" /> Property URI Value string Encoding Scheme URI Value URI

23 Using the DC-XML format
Supports only limited subset of Abstract Model (revision forthcoming) The container element, here <meta>, represents a single DC description. Each child element represents a single statement Property URIs and Encoding Scheme URIs encoded as XML QNames <?xml version="1.0"?> <meta xmlns="http://www.ukoln.ac.uk/metadata/dcdot/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dc="http://purl.org/dc/elements/1.1/"> <dc:identifier>http://example.org/doc/1234/</dc:identifier> <dc:title>A Guide to DC Metadata</dc:title> <dc:language xsi:type="dcterms:ISO639-2">eng</dc:language> <dcterms:references>http://dublincore.org/documents/dcq-html</dcterms:references> </meta> Property URI Value string Encoding Scheme URI

24 Using the Resource Description Framework (RDF)
Specifications for DC in RDF do exist… … but currently work in progress to resolve ambiguities revise in light of DCAM

25 Dublin Core Application Profiles
For full details see the DCMI recommendations and Andy Powell's tutorial

26 DC Application Profile
Implementers adapt metadata standards to the context of their application Tension between localisation and interoperability A DC Application Profile specifies the terms (properties, vocabulary/syntax encoding schemes) used in a class of description sets describes how those terms are used supplementary information on how properties applied/interpreted in context constraints on occurrence of properties constraints on values and value representations (encoding schemes)

27 DC Application Profiles: Examples
"Simple Dublin Core" use of the 15 properties of the DCMES all optional and repeatable values represented by value strings no vocabulary or syntax encoding schemes UK eGMS use of selected properties from DCMI vocabularies, additional properties guidelines on use of properties some properties mandated/recommended some vocabulary encoding schemes mandated/recommended guidance on content of value strings

28 DC Application Profiles: Examples
JISC Information Environment Service Registry (IESR) Metadata Schema supports description of several related resources (Collection, Service, Agents) use of selected properties from DCMI vocabularies, selected properties from RSLP CD vocabularies, some properties created for IESR for each subject resource type, guidelines on use of properties some properties mandated/recommended many vocabulary encoding schemes mandated/recommended

29 DCMI Vocab Encoding Schemes DC Application Profile A: "Simple DC"
DCMI Properties DCMI Vocab Encoding Schemes DC Application Profile A: "Simple DC" DC Application Profile B: IESR IESR Properties IESR Vocab Encoding Schemes "Mixing and matching"

30 DC in Practice

31 Dublin Core in X/HTML Initial implementation focused on DC-in-HTML
Robot crawls individual HTML pages to extract metadata But today little/no use by large Web search engines Problems of spamming/trust Lack of take-up by authors/publishers Success of full-text crawling/indexing, esp. Google! However, some use in controlled domains Intranets Trusted groups of providers (e.g. eGMS) Embedding DC in XHTML useful if you know a search engine exploits it

32 Harvester HTTP GET Web Sites

33 Picture Australia - images "related to all things Australian" from 40+ cultural agencies"
central search service based (initially at least) on crawling HTML-embedded DC metadata providers migrating to OAI-PMH currently hybrid approach?

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35

36 Dublin Core and OAI-PMH
Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) Fairly simple mechanism for sharing metadata records between applications Has origins in “e-prints” community Built on HTTP, XML Allows a harvester to ask a repository for all or some of its metadata records (in a specified metadata format) i.e. supports "incremental harvesting" "Give me all your records updated since yyyy-mm-dd" "OAI-DC" (Simple DC) is mandatory format But no limitation on format that can be transferred (as long as can be described by XML Schema)

37 Harvester OAI-PMH Repositories

38 OAIster (University of Michigan)
"academically-oriented digital resources" "5,947,627 records from 557 institutions" ( )

39 1984 results! Notice different value strings for of DC elements e.g. format, subject So limited in terms of services that can be offered

40 Follow link through to source site

41 Summary DCMES/"Simple DC" as a "core" for discovery of wide range of resources "Simple DC" is, by definition, simple! Limitations in terms of functions/services that can be offered DCMI Abstract Model provides a framework for extensibility and modularity A DC Application Profile describes a real-world usage of that model

42 An Introduction to Dublin Core
Making Sense of Metadata, Society of Archivists EAD/Data Exchange SIG London, Thursday 17 November 2005 Pete Johnston Research Officer, UKOLN, University of Bath UKOLN is supported by:


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