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=" /> <link rel="schema.DCTERMS" href=" />
<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=" />
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=" xmlns:xsi=" xmlns:dc="
<dc:identifier>
<dc:title>A Guide to DC Metadata</dc:title>
<dc:language xsi:type="dcterms:ISO639-2">eng</dc:language>
<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?

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: