An abstract model for DCMI metadata descriptions

An abstract model for DCMI metadata descriptions

Andy [email protected]

UKOLN, University of Bath, UKhttp://www.ukoln.ac.uk/

UKOLN is supported by:

DC Usage Board meeting at DC2003, SeattleSeptember/October 2003

http://creativecommons.org/licenses/by/1.0/

DC-2003 - Seattle, Sept/Oct 20032

I am going to…

• assume people have read the current ‘Abstract Model’ working draft

• propose a revised (more generic) abstract model

• look at some of the issues that have been raised

• encourage discussion of the revised model and the issues

• consider what happens next with the abstract model document


Major issues

• why develop an abstract model?• what is ‘qualified DC’? why

limit to DCMI properties?• what is a ‘record’?• what is ‘simple DC’? why limit to DCMES• what is a ‘value’?• where does DCSV fit in?• relationship to ‘application profiles’?• relationship to RDF?• abstract model and dumb-down?


Why?• non-syntax-based view of what constitutes

a DC metadata description• need to understand what kinds of

descriptions we are trying to encode• best done without reference to any

particular syntax• allows us to compare and contrast the

capabilities of different encodings• syntax X supports feature Y but syntax Z

doesn’t

• supports better mappings between syntaxes


What is qualified DC?

• general feeling that limiting abstract model for ‘qualified DC’ to DCMI properties is too limiting

• real world applications typically go beyond this

• therefore, need to re-model at more generic level• DCMI Abstract Model

frankly my dear, I

don’t give a DAM


DCMI abstract model

• a description is made up of one or more properties and their associated values

• each property is an attribute of the resource being described

• properties may be repeated• a record is a set of descriptions about

one or more related resources

therefore… each description is about one, and only one, resource (the 1:1 principle)

use of the word record may be a problem?


DCMI abstract model (2)

• each value is a resource• each value may be denoted by a value

string• each value string may have an

associated encoding scheme • each encoding scheme is identified by

an encoding scheme URI • each value string may have an

associated language (e.g. en-GB)

a value string is a ‘simple’, human-readable string


DCMI abstract model (3)

• each value may be identified by a value URI

• each value may have an associated rich value (some marked-up text, an image, a video, some audio, etc. or some combination thereof)

• each value may have some associated related metadata

related metadata is a description of a related resource – e.g. metadata about the person who is the creator of a document…


What is a record?

• a record is a set of descriptions about one or more related resources, e.g.• a description of a resource and a

description of its creator• a description of a resource, a rights

statement about the resource and a description of the description

• note: a description is about a single resource and is made up of one or more properties and their associated values


What is a value?• a value is the physical or conceptual entity

that is associated with a property when it is used to describe a resource• a person (physical)• an organisation (physical)• a subject (conceptual)• a country (physical)• a type (conceptual)• etc.

• therefore, in the abstract model,a value is always a resource


A value is always a resource

• in the DCMI abstract model, a value is always a resource

• the value resource may• be identified by a value URI• be denoted by a string value and/or a

rich value• have some associated related metadata

• …but the value is always a resource!• I think this has an impact on the RDF

encodings??


But some problems…

• some problems with wording of existing DCMES definitions…

• CCP element values defined to be a ‘…resource…’

• relation, identifier and source defined to be a ‘…reference to a resource…’

• rights defined to be either a ‘…resource…’ or a ‘link to a service that provides a resource…’

• problem: too much of the model is embedded into the definition!


What is qualified DC?

• a ‘qualified DC record’ is …• any record that

• conforms to the DCMI abstract model

• contains a description that uses at least one DCMI term

however, this means that it is probably not possible to define a single XML schema for qualified DC records – but can provide a template XML schema


What is simple DC?

• a ‘simple DC record’ is …• any record that

• conforms to the DCMI abstract model

• comprises only a single description• uses only properties taken from

DCMES• makes no use of value URIs,

encoding schemes, rich values or related metadata


…or to put it differently

• a simple DC record is made up of a single description

• that description is made up of one or more properties and their associated values

• each property is an attribute of the resource being described

• each property must be one of the 15 DCMES elements

• properties may be repeated • each value is denoted by a value string • each value string may have an associated

language (e.g. en-GB)


…or to put it differently

• simple DC is an ‘application profile’ that only uses terms taken from the DCMES


simple DC and value URIs

• all values in simple DC are denoted using only a value string

• the value string can be a URI…• …but there is nothing to formally

indicate that the value string is a URI• simple DC software applications may

choose to guess which value strings are URIs and which aren’t


Simple DC and audience

• why isn’t dcterms:audience included in ‘simple DC’?

• because single namespace is simpler than multiple namespaces• dc:xxx and dcterms:xxx

• because static definition is simpler than one that grows over time• audience + … + …

• because, arguably, audience not part of the ‘core’

• the ‘t-shirt’ problem


Abstract model and DCSV?

• DCSV provides mechanism for encoding ‘markup’ in value string

• thus DCSV runs slightly counter to the abstract model

• DCSV better handled as ‘related metadata’• e.g. Period provides related metadata

about a conceptual ‘period in time’• impact? XML enc. good – string enc. bad?

• suggest no new proposals based on DSCV for the time being


What is a DCAP?

• a Dublin Core Application Profile (as currently defined) declares the properties and encoding schemes used to construct a description as used within a particular application

• problems…• DCAPs don’t currently cover the

whole abstract model• DCAPs define what a description is –

but most ‘applications’ need defining at the record level


RDF vs. abstract model

• what is the relationship between RDF and the abstract model?

• RDF provides richest encoding syntax currently

• full encoding of all features of the model

• but expect to see model fully implemented in XML as well

• (expect HTML syntax to always be a partial implementation)


Dumb-down• intelligent vs. dumb, element vs. value• element dumb-down (dumb)

• ignore anything that isn’t [DCMES/an element]

• element dumb-down (intelligent)• resolve sub-properties until you get to [DCMES/an

element]

• value dumb-down (dumb)• use value URI or value string as value string

• value dumb-down (intelligent)• use knowledge of related metadata, or value string

to create new value string• resolve sub-classes/broader terms


sub-properties and classes

• RDFS and human-readable declarations of DCMI terms refer to sub-properties and sub-classes

• however, these don’t formally appear in the abstract model (expect as part of dumb-down)

• where do these fit into the model?• I think they belong in the

‘grammatical principles’ document



Example 1 – dc:creator

<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:my="http://purl.org…"> <rdf:Description> <dc:creator> <rdf:Description> <rdf:value> Andy Powell </rdf:value> <my:email> [email protected] </my:email> </rdf:Description> </dc:creator> </rdf:Description></rdf:RDF>

Example RDF description using dc:creator…




dc:creator

Andy Powell…

my:affiliation a.powell@uko…

my:email

…and the RDF model it represents.

UKOLN, Univ…

a.powell@uko…

Andy Po…

rdfs:label

my:name




dc:creator

Andy Powell…


my:email

UKOLN, Univ…

a.powell@uko…

Andy Po…

rdfs:label

my:name

But… we don’t want to embed all this information

into every instance metadata record do we?

relatedMetadata


<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:my="http://purl.org…"> <rdf:Description> <dc:creator> <rdf:Description> <rdf:value> Andy Powell </rdf:value> </rdf:Description> </dc:creator> </rdf:Description></rdf:RDF>


dc:creator

Andy Powell…

rdfs:label

<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:my="http://purl.org…"> <rdf:Description> <my:name> Andy Powell </my:name> <my:email> [email protected] </my:email> </rdf:Description></rdf:RDF>


my:email

UKOLN, Univ…

a.powell@uko…

Andy Po…

my:name

Need to separate part of the information out and store it

in a single place – in this case in a directory service…




valueURI

dc:creator

Andy Powell…

rdfs:label


valueURI


my:email

UKOLN, Univ…

a.powell@uko…

Andy Po…

my:name

To do this we need to assign a URI (the ‘valueURI’) to the anonymous ‘value’ node…




valueURI

dc:creator

Andy Powell…

rdfs:label


valueURI


my:email

UKOLN, Univ…

a.powell@uko…

Andy Po…

my:name

relatedMetadataURI

The document containing this information is itself an

RDF resource (the ‘relatedMetadata’) and has

a URI




valueURI

dc:creator

Andy Powell…

rdfs:label


valueURI


my:email

UKOLN, Univ…

a.powell@uko…

Andy Po…

my:name

relatedMetadataURI

rdfs:seeAlso

Use rdf:seeAlso to form linkage between description

and relatedMetadata…


Example 2 – dc:subject

<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:dcterms="http://purl.org…"> <rdf:Description> <dc:subject> <dcterms:MESH> <rdf:value> D08.586.682.075.400 </rdf:value> <rdfs:label> Formate Dehydrogenase </rdfs:label> </dcterms:MESH> </dc:subject> </rdf:Description></rdf:RDF>

Example RDF description using dc:subject (taken

from Qualified DC in RDF recommendation…




dcterms:MESH

dc:subject

rdf:type D08.586…rdf:type

rdfs:label

Formated…

rdfs:value

…and the RDF model it represents.




dcterms:MESH

dc:subject

rdf:typerdf:type

But… we don’t want to embed all this information

into every instance metadata record do we?

relatedMetadata

D08.586…

rdfs:label

Formated…

rdfs:value



<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:dcterms="http://purl.org…"> <rdf:Description> <dc:subject> <dcterms:MESH> <rdf:value> D08.586.682.075.400 </rdf:value> </dcterms:MESH> </dc:subject> </rdf:Description></rdf:RDF>

dcterms:MESH

dc:subject

rdf:typerdf:type

<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:dcterms="http://purl.org…"> <dcterms:MESH> <rdf:value> D08.586.682.075.400 </rdf:value> <rdfs:label> Formate Dehydrogenase </rdfs:label> </dcterms:MESH></rdf:RDF>dcterms:MESH

D08.586…

Formated…

Need to separate part of the information out and store it

in a single place – in this case with the terminology

owner…

rdfs:label

Formated…




valueURI

dcterms:MESH

dc:subject

rdf:typerdf:type

<?xml version="1.0"?><rdf:RDF xmlns:rdf=http://www….xmlns:rdfs=http://www.w3.org/…xmlns:dc=http://purl.org/dc/…xmlns:dcterms="http://purl.org…"> <dcterms:MESH> <rdf:value> D08.586.682.075.400 </rdf:value> <rdfs:label> Formate Dehydrogenase </rdfs:label> </dcterms:MESH></rdf:RDF>

valueURI

dcterms:MESH

D08.586…

Formated…

To do this we need to assign a URI (the ‘valueURI’) to the anonymous ‘value’ node…

rdfs:label

Formated…




valueURI

dcterms:MESH

dc:subject

rdf:typerdf:type


valueURI

dcterms:MESH

D08.586…

Formated…

relatedMetadataURI

The document containing this information is itself an

RDF resource (the ‘relatedMetadata’) and has

a URI

rdfs:label

Formated…




valueURI

dcterms:MESH

dc:subject

rdf:typerdf:type


valueURI

dcterms:MESH

D08.586…

Formated…

relatedMetadataURI

rdfs:seeAlso

Use rdf:seeAlso to form linkage between description

and relatedMetadata…

rdfs:label

Formated…


Abstract DC model


valueURI

dcterms:MESH

dc:subject

rdf:typerdf:type


valueURI

dcterms:MESH

D08.586…

Formated…

relatedMetadataURI

rdfs:seeAlso

resource

property

valueURI

valueString

In terms of abstract DC model we now have: resource,

property, valueURI, valueString (and valueStringLang), encodingScheme, relatedMetadata

resource

property

valueURI

relatedMetadata

encodingScheme

rdfs:label

Formated…

valueString(valueStringLang)

Documents

An abstract model for DCMI metadata descriptions