Everything you wanted to know about Dublin Core metadata

24

Ap

ril 20

08

Pete Johnston & Andy Powell, Eduserv [email protected]

[email protected]://www.eduserv.org.uk/foundation

Everything you wanted to know about Dublin Core metadata but…

Tutorial for Eduserv Staff, Bath

24 April 2008Tutorial for Eduserv staff, Bath 2

Dublin Core, the DCMI Abstract Model &DC Application Profiles

Title slide photo “Orange flavour” by Flickr user kinderuSee http://www.flickr.com/photos/kinderu/2328911735/Made available under CC Attribution-NonCommercial-Share-Alike 2.0 license

http://www.flickr.com/photos/kinderu/2328911735/

http://creativecommons.org/licenses/by-nc-sa/2.0/deed.en_GB




Show of Hands

• Designing/developing metadata applications?

• Designing/developing Dublin Core metadata applications?

• Heard of the DCMI Abstract Model?

• Read the DCMI Abstract Model?

• Familiar with RDF?

• Designing/developing RDF applications?


Everything you wanted to know about Dublin Core metadata but...

• “Dublin Core” in c.2003

• The DCMI Abstract Model– DCAM & RDF

• Syntax: “Encoding” Dublin Core metadata

• Context & Constraints: “DC Application Profiles” & the Singapore Framework

• Example: The Scholarly Works (ePrints) DC Application Profile (SWAP)

• “Dublin Core” in 2008


“Dublin Core” in c.2003

• Metadata vocabularies– … but what is a DC “element”?

• Syntax independence & encoding guidelines– … but what are we “encoding”?

• “Simple” and “Qualified” DC– … vocabularies?– … formats? (e.g. oai_dc)– … constraints on use of vocabularies? On which vocabularies?

• DC application profiles– … “(re)using” terms? But what “terms” can we “(re)use”?

• Grammatical Principles• DC & the Resource Description Framework• Absence of domain model(s)

– the “checklist” approach to DC implementation


The DCMI Abstract Model



• Work on DCAM by DCMI Architecture Community from mid-2003, initiated by Andy Powell

• Initial Version, DCMI Recommendation, 2005-03-07

• Second Version, DCMI Recommendation, 2007-06-04

– http://dublincore.org/documents/2007/06/04/abstract-model/

http://dublincore.org/documents/2007/06/04/abstract-model/



DCAM and Resources

• 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



• DCAM describes– Components and constructs that make up an

information structure (“DC description set”)

– How that information structure is to be interpreted

• Made up of three related “information models”

– Resource model

– Description set model

– Vocabulary model



• DCAM describes an information structure called a “description set”…

• …but does not describe how to represent DC description set in concrete form

– DCMI-defined “Encoding guidelines”

– Formats defined by others, e.g. Eprints DC-XML

• DCAM describes various types of metadata term…

• …but does not specify the use of any fixed set of terms

– DCMI-owned metadata vocabularies

– Vocabularies owned/defined by other agencies


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; simplified entity-relational model


DCAM Description Set Model



• The structure of “DC metadata”• Uses URIs to refer to resources described & to 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

Description Set

Description

Statement

Property URI

Resource URI

Literal Value Surrogate

Description

Statement

Property URI

Resource URI

Non-Literal Value Surrogate

Statement

Property URI




• 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

• 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

Description Set

Description

Statement

Property URI

Resource URI


Description

Statement

Property URI

Resource URI


Statement

Property URI


Value URI

Vocab Enc Scheme URI

Value URI

Value string

Value string Syntax Enc Scheme URI

Language

Value string Language



• a value may be described by another description

Description Set

Description

Statement

Property URI

Resource URI


Description

Statement

Property URI

Resource URI


Statement

Property URI


Value URI


Value URI

Value string

Value string

Value string

Syntax Enc Scheme URI

Language

Language

Description Set

Description

Statement

Property URI


Description

Statement

Property URI

Resource URI


Statement

Property URI



Value URI

Value string

Value string

Value string

Syntax Enc Scheme URI

Language

Language


Description sets & RDBMS

• Not a perfect analogy, but…– URIs as keys to tables

– Each description = (roughly) a row in a table

– Each statement = (roughly) a field name and field content

– Each literal value surrogate = field content (possibly typed)

– Each non-literal value surrogate = secondary key (value URI) and/or data from secondary table

– Description set = some set of rows which it is useful to bundle together

Description Set

Description

Statement

Property URI

Resource URI

Example: Description set with two descriptions, statements with non-literal value surrogates & literal value surrogates

Statement

Property URI




Value URI

Value string

Value string

Value URI

Language

Language

Description

Resource URI

Statement

Property URI


Value string Language

Description Set

Description

Statement

Statement

<http:/purl.org/dc/terms/subject>



<http://example.org/terms/mySH>

“Metadata”

"Métadonnées"

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 URIProperty URI


Value String

Value String

Description

Statement

<http://example.org/org/DCMI>

<http://xmlns.com/foaf/0.1/name>


“Dublin Core Metadata Initiative” en Value StringProperty URI

Example: Description set with two descriptions, statements with non-literal value surrogates & literal value surrogates

@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) ) ) ))


DCAM & RDF


DCAM & RDF

• A history of co-evolution• DCAM grounded in concepts of RDF

– i.e. assertions of binary relationships between resources– (rather informally!) shares RDF Semantics– basis for merging, inferencing– DCAM Vocabulary Model is RDF Schema

• Doesn’t explicitly use “description model” of RDF (triple, graph)

• Mapping from DCAM description model to RDF graph provided by “Expressing DC metadata using RDF”, DCMI Recommendation, 2008-01-14

• (Tentative) plans to revise DCAM to base more formally on RDF model


Further references

• Powell, Nilsson, Naeve, Johnston, Baker. DCMI Abstract Modelhttp://dublincore.org/documents/2007/06/04/abstract-model/

• Klyne, Carroll. RDF Concepts and Abstract Syntaxhttp://www.w3.org/TR/rdf-concepts/

• Nilsson, Johnston, Naeve, Powell. “Towards an Interoperability Framework for Metadata Standards”. DC-2006http://www.dublincore.go.kr/dcpapers/pdf/2006/Paper39.pdf

• Nilsson (ed), Harmonization of Metadata Standards. ProLEARN Projecthttp://ariadne.cs.kuleuven.be/lomi/images/5/52/D4.7-prolearn.pdf



http://www.w3.org/TR/rdf-concepts/

http://www.dublincore.go.kr/dcpapers/pdf/2006/Paper39.pdf

http://www.dublincore.go.kr/dcpapers/pdf/2006/Paper39.pdf


Syntax: “Encoding” Dublin Core metadata


“Encoding” Dublin Core metadata

• DCAM description model is syntax-independent• For transfer between applications, descriptions must

be encoded as digital objects (records) • “Encoding Guidelines” describe

– how abstract information structure is serialised/encoded using a metadata format

– how instances of a metadata format are decoded/interpreted in terms of abstract information structure

• Provider and consumer need shared rules for encoding/decoding

• DCAM description set as “interface”; concrete syntax as implementation

System A

DC DescriptionSet

DC-XMLInstance

Encode usingBinding

Construct usingDCAM & DSP

Decode usingBinding

DC DescriptionSet

Interpret usingDCAM

System B

DC-XMLInstance

<?xml version="1.0"?><dcx:descriptionSet>



• Multiple syntaxes available– Defined by DCMI– Defined by other parties

• Different syntaxes may be appropriate for different contexts

• “Encoding guidelines” specify– what subset of DCAM description model supported– how each supported feature of DCAM encoded as

syntactic constructs– how syntactic constructs interpreted as DCAM

features



• Warning!

• Some of current DCMI “Encoding Guidelines” specs– Pre-date development of DCAM

– Use earlier, simpler “DC abstract models”

– Not fully compatible with DCAM description set model

• Updating of specs in progress (2008)

• Meanwhile, some formats defined outside of DCMI– e.g. Eprints DC-XML


DC-RDF

• “Expressing DC metadata using RDF”, DCMI Recommendation, 2008-01-14

– http://dublincore.org/documents/2008/01/14/dc-rdf/

– Uses RDF abstract syntax

– Supports full DCAM description model

– Multiple concrete syntaxes available for RDF• RDF/XML, N3, Turtle, RDFa etc

– Stable, complete

– Example RDF/XML instance

http://dublincore.org/documents/2008/01/14/dc-rdf/

http://dublincore.org/documents/2008/01/14/dc-rdf/


DC-XML-Full

• “Expressing DC metadata using XML (DC-XML-Full)”, Working Draft, 2007-06-19

– http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLFGuidelines/2007-06-19

– Supports full DCAM description model– Verbose, but easily processable– GRDDL Namespace Transformation to generate

RDF/XML– To be moved forward (as Proposed Recommendation?),

err, some time soon….– Example instance documents

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLFInstances/2007-06-19

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLFGuidelines/2007-06-19

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLFGuidelines/2007-06-19


DC-XML-Min

• “Expressing DC metadata using XML (DC-XML-Min)”, Working Draft, 2007-06-19

– http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLMGuidelines/2007-06-19

– Supports subset of DCAM description model– More compact, but more options to handle– Use of QNames for URIs makes it slightly difficult to use

with W3C XML Schema– GRDDL Namespace Transformation to generate

RDF/XML– To be revised, need clearer requirements– Example instance document

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLMInstances/2007-06-19

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLMGuidelines/2007-06-19

http://dublincore.org/architecturewiki/DCXMLRevision/DCXMLMGuidelines/2007-06-19


DC-HTML

• “Expressing DC metadata using HTML/XHTML meta and link elements”, Proposed Recommendation, 2007-11-05

– http://dublincore.org/documents/2007/11/05/dc-html/– Supports subset of DCAM description model– DC metadata in HTML document describes that document

• or at least document of which HTML page is representation – An HTML meta-data profile– GRDDL Profile Transformation to generate RDF/XML– Minor amendments required– To be moved forward as Proposed Recommendation soon….– Example instance document

http://dublincore.org/documents/2007/11/05/dc-html/ex34/– Triples

http://dublincore.org/documents/2007/11/05/dc-html/


DC-Text

• “Expressing DC metadata using DC-Text”, DCMI Recommended Resource, 2007-12-03

– http://dublincore.org/documents/2007/12/03/dc-text/

– Supports full DCAM description model

– Intended for human-readability rather than machine-processing

– Used in documentation etc

– Stable, complete

– (Example instance earlier in presentation)

http://dublincore.org/documents/2007/12/03/dc-text/


Further references

• Nilsson. Basic Syntaxes. Tutorial at DC-2007http://dc2007.sg/T2-BasicSyntaxes.pdf

• DCMI Architecture Community Jiscmail listhttp://www.jiscmail.ac.uk/lists/DC-ARCHITECTURE.html


Context & Constraints:The DCAM & “DC application profiles”


“DC application profiles”

• Notion of “DC application profile” widely used within DCMI and by DC implementers

– Customisation to meet needs of community/domain– Typically annotated lists of selected terms to be used in DC

metadata– Terms defined by DCMI or by other agencies

• But…– Absence of “domain model”

• Tendency to model of world of homogeneous objects

– Focus exclusively on vocabulary• A “checklist” approach to DCAPs

– Over-emphasis on 15 properties of DCMES/”Simple DC” • Tendency to try to bend/extend 15 properties beyond their

intended use….• …or reject DC as not useful


The DCAM & DC Application Profiles

• Specification of how to construct description sets (descriptions, statements) to serve some purpose

• At core, a profile of a “description set”– a set of constraints– based on E-R model of problem space

• A DC Application Profile is “packet of documentation” which consists of:

– Functional requirements (desirable)– Domain model (mandatory)– Description Set Profile (DSP) (mandatory)– Usage guidelines (optional)– Encoding syntax guidelines (optional)


DCMI Description Set Profile (DSP)

• A way of describing structural constraints on a description set

– the resources that may be described by descriptions in the description set

– the properties that may be referenced in statements

– the ways a value surrogate may be given

• Description templates, statement templates

• Model & XML Syntax for DSP– Working draft by Mikael Nilsson (Royal Institute of

Technology, Sweden)

– http://dublincore.org/documents/2008/03/31/dc-dsp/

http://dublincore.org/documents/2008/03/31/dc-dsp/

24 April 2008Tutorial for Eduserv staff, Bath 43Foundation standards

Domain standards

Application Profile

The “Singapore Framework”


Further references

• Nilsson, Baker, Johnston. The Singapore Framework for Dublin Core Application Profileshttp://dublincore.org/documents/2008/01/14/singapore-framework/

• Nilsson. Description Set Profiles: A constraint language for Dublin Core Application Profileshttp://dublincore.org/documents/2008/03/31/dc-dsp/


Example: The Scholarly Works (ePrints) DC Application Profile (SWAP)


Background to the Eprints DCAP

• Eprints AP development funded by JISC, Summer 2006

• Co-ordinated by Julie Allinson (UKOLN) & Andy Powell (Eduserv Foundation)

• "eprint":

– a ''scientific or scholarly research text'‘ (Budapest Open Access Initiative)

– e.g. peer-reviewed journal article, preprint, working paper, thesis, book chapter, report, etc.

• Specification for using DC metadata for eprints that overcomes limitations of "Simple DC“

– especially relationships between “versions”

– “what is being described?”


Components

• Functional requirements specification• Domain model

– Based on subset of FRBR

• The "eprints DCAP"– a "Description Set Profile"

– plus human-readable commentary, usage guidelines

• New vocabularies of metadata terms– With URIs like http://purl.org/eprint/terms/xyz

• Eprints DC-XML XML format– Based on DC-XML-Full, Version 2006-09-18


• Report of IFLA Study Group, 1998• Entity-Relational model for the “world” that

bibliographic records describe• FRBR models the world using 4 key entities (Group 1

Entities):– a work is a distinct intellectual or artistic creation. A work is an

abstract entity – an expression is the intellectual or artistic realization of a

work– a manifestation is the physical embodiment of an expression

of a work – an item is a single exemplar of a manifestation. The entity

defined as item is a concrete entity

• Primary relationships – Work -- is realized through --> Expression

– Expression -- is embodied in --> Manifestation

– Manifestation -- is exemplified by --> Item

Functional Requirements for Bibliographic Records (FRBR)


FRBR Group 1 Entities

Work

Expression1..∞

isRealisedThrough

Manifestation

isEmbodiedIn

∞..∞

Copy

isExemplifiedBy

1..∞


• Work-Work Relationships– Successor, Supplement, Adaptation etc

– Whole-Part

• Expression-Expression Relationships– Abridgement, Revision, Translation etc

– Whole-Part

• Manifestation-Manifestation Relationships– Reproduction, Alternate

– Whole-Part

• Item-Item Relationships– Reconfiguration, Reproduction

– Whole-Part



• Group 2 Entities: Person, Corporate body

– Responsibility relationships

• Work is-Created-By Person/CB

• Expression is-Realised-By Person/CB

• Manifestation is-Produced-By Person/CB

• Item is-Owned-By Person/CB

• Group 3 Entities: Concept, Object, Event and Place

– Subject relationships

• Work has-as-Subject Work/Expression/Manifestation/Item

• Work has-as-Subject Person/CB

• Work has-as-Subject Concept/Object/Event/Place


The eprints DCAP Domain Model

ScholarlyWork

Expression0..∞

isExpressedAs

Manifestation

isManifestedAs

0..∞

Copy

isAvailableAs

0..∞

0..∞

0..∞

isCreatedBy

isPublishedBy

0..∞isEditedBy

0..∞isFundedBy

isSupervisedBy

AffiliatedInstitution

Agent

The eprints DCAP Domain Model

Expression

isExpressedAs

Expression

isExpressedAs

Manifestation Manifestation

isManifestedAs isManifestedAs

hasVersion

hasTranslation

hasAdaptation

Copy

isAvailableAs

Copy

isAvailableAs

Copy

isAvailableAs

ScholarlyWork

ePrints DCAP attributes/properties (sample)

ScholarlyWork:titlesubjectabstractaffiliated institutionidentifier

ScholarlyWork:titlesubjectabstractaffiliated institutionidentifier

Agent:nametype of agentdate of birthmailboxhomepageidentifier

Agent:nametype of agentdate of birthmailboxhomepageidentifier

Expression:titledate availablestatusversion numberlanguagegenre / typecopyright holderbibliographic citationidentifier

Expression:titledate availablestatusversion numberlanguagegenre / typecopyright holderbibliographic citationidentifier

Manifestation:formatdate modified

Manifestation:formatdate modified

Copy:date availableaccess rightslicenceidentifier

Copy:date availableaccess rightslicenceidentifier


The eprints DCAP as DSP

• Developed initially using "traditional" "tabular" DCAP presentation

• Retrospectively used as test case for DSP model• Document divided into five sections/tables, one for description

of each entity type– -> DSP Description Template

• Each section/table divided into rows, one for each statement type within description

– -> DSP Statement Template

• For statement referencing Literal Value– -> DSP Literal Value Constraint

• For statement referencing Non-Literal Value– -> DSP Non-Literal Value Constraint

http://www.ukoln.ac.uk/repositories/digirep/index/EPrints_Application_Profile





Thoughts on the Approach (Julie Allinson)

• Driven by the functional requirements identified

• Makes it easier to rationalise ‘traditional’ and ‘modern’ citations

– traditional citations tend to be made between eprint ‘expressions’

– hypertext links tend to be made between eprint ‘copies’ (or ‘items’ in FRBR terms)

• A complex underlying model may be manifest in relatively simple cataloguer and/or end-user interfaces

• Existing eprint systems may well capture this level of detail currently – but emphasis on simple DC stops them exposing it to others!


Further references

• Allinson, Powell. Eprints Application Profilehttp://www.ukoln.ac.uk/repositories/digirep/index/Eprints_Application_Profile

• Allinson, Johnston, Powell. “A Dublin Core Application Profile for Scholarly Works” Ariadne50 (Jan 2007)http://www.ariadne.ac.uk/issue50/allinson-et-al/

• IFLA. Functional Requirements for Bibliographic Records. 1998, 2007http://www.ifla.org/VII/s13/frbr/


Dublin Core in 2008


Dublin Core in 2008

• 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

• a vocabulary model & support for defining additional vocabularies of terms

• which can be referenced in statements• a profile model & support for defining DC application profiles

– which describe how to construct description sets for some particular set of requirements

• extensibility, modularity, structural validation, compatibility with Semantic Web


Dublin Core in 2008

• Current DCMI work in progress• Generally, shift from focus on vocabularies to framework and

its use in DCAPs• Updating “encoding guidelines” for DC-XML, DC-HTML• Finalising Description Set Profile model & syntax• Developing guidelines for creating DCAPs (including DSPs)• Working with IEEE LOM community on expressing LOM

metadata using DCAM• Working with library community on revision of core library

metadata standards in RDA initiative (using FRBR & DCAM)• Future?

• Sort out messy documentation!• Clarify formal relationship between DCAM and RDF?• New “encoding guidelines” for e.g. RDFa?• DC metadata as Linked Data?• Relationship to “informal metadata” (tagging etc)?

24

Ap

ril 20

08

Pete Johnston & Andy Powell, Eduserv [email protected]

[email protected]://www.eduserv.org.uk/foundation

Everything you wanted to know about Dublin Core metadata but…

Tutorial for Eduserv Staff, Bath

Business

Everything you wanted to know about Dublin Core metadata