DC Architecture WG meeting Monday Sept 12 Slot 1: 15.30 - 17.00 Slot 2: 17.30 - 19.00 Location: Seminar Room 4.1.E01.

DC Architecture WG meeting

Monday Sept 12Slot 1: 15.30 - 17.00Slot 2: 17.30 - 19.00

Location: Seminar Room 4.1.E01.

Agenda

review of the year revised "DCMI Namespace Policy"

recommendation revising "Guidelines for encoding

DC in XML“ recommendation summary of relevant W3C

activities (GRDDL and RDF in XHTML) (*)

workplan for next year

Review of the year

Progress during 2005

DCMI Abstract Model document issued as a Recommendation

agreed persistent URIs for the latest version of our XML schemas

developed draft revised "DCMI Namespace Policy“

proposed changes to XML guidelines set up task force to look at DC/RDF

issues

Revised DCMI namespace policy

Revised Namespace Policy

new draft policy is available at:http://www.ukoln.ac.uk/metadata/dcmi/namespace-policy/

New terminology

partly to remove confusion with XML namespaces– DCMI namespace - A collection of DCMI term

URIs where each term is assigned a URI that starts with the same 'base URI'. The 'base URI' is known as the DCMI namespace URI. (Note that a DCMI namespace is not the same as an 'XML namespace')

– DCMI namespace URI - The URI that identifies a DCMI namespace

– vocabulary - A collection of terms (often as used in the context of an 'applicationprofile')

Namespaces vs. vocabularies

note that the grouping of term URIs into a DCMI namespace is orthogonal to the grouping of terms into a vocabulary

term URIs are grouped into DCMI namespaces in order to ease the assignment of URIs to terms and to streamline their use in particular encoding syntaxes

terms are grouped into vocabularies in order to meet a functional need

However…

…we quite clearly haven't done this in the case of the DC and DCTERMS namespaces

we have kept two namespaces simply for historical reasons

therefore suggest replicating all the current terms in the DC namespace into the DCTERMS namespace, using RDFS/OWL to explicitly declare equivalences as necessary

XML encoding guidelines

Summary of relevant W3C activities

Summary of DC RDF Taskforce activities

DC RDF Taskforce

Clarification of the recommendations for encoding 'value strings' in DC RDF/XML

Guidelines for encoding DC metadata using the RDF Model

DC Property Domains and Ranges Proposed changes to DCMI

property definitions DCMI Term Decision Tree

DC RDF Taskforce





Encoding DC using RDF Model

leading towards new DCMI Recommendation

replacing the current Simple DC in RDF Recommendation and Qualified DC in RDF Proposed Recommendation

mapping from DCMI Abstract Model to RDF Model– therefore can use current and future

RDF syntaxs (XML, N3, etc.)

DCMI abstract model

a description is made up of– one or more statements (about one, and

only one, resource) and– optionally, the URI of the resource being

described (resource URI )

each statement is made up of– a property URI (that identifies a property)– a value URI (that identifies a value) and/or

one or more representations of the value (value representations)

Value strings

each value representation may take the form of a value string, a rich value or a related description

each value string is a simple, human-readable string that represents the resource that is the value of the property

each value string may have an associated value string language that is an ISO language tag (e.g. en-GB)

Encoding schemes

values and value strings can be ‘qualified ’ by using encoding schemes

a vocabulary encoding scheme is used to indicate the class of the value– e.g. the value is taken from LCSH

a syntax encoding scheme is used to indicate how the value string is structured– e.g. the value string is a date structured

according to the W3CDTF rules (“2004-10-12”)

Description sets

real-world metadata applications tend to be based on loosely grouped sets of descriptions (where the described resources are typically related in some way)

known in the abstract model as description sets

for example, a description set might comprise descriptions of both a painting and the artist

Records

description sets are instantiated, for the purposes of exchange between software applications, in the form of metadata records

each record conforms to one of the DCMI encoding guidelines (XHTML meta tags, XML, RDF/XML, etc.)

<dc:title>a document</dc:title><dc:creator>andy powell</dc:creator>

record

Model summaryrecord (encoded as XHTML, XML or RDF/XML)

description set

description (about a resource (URI))

statement

property (URI) value (URI)

representation

value string

OR rich value

OR related description

vocabulary encoding scheme (URI)

syntax encodingscheme (URI)

language(e.g. en-GB)

resourceURIpropertyURI

valueURIrdfs:label

“value string”

propertyURIvalueURI

rdfs:label“value string”

propertyURIvalueURI

Description

rdf:type vocabularyEncodingSchemeURI

Statement

statement


valueURIrdfs:label

“value string”

propertyURIvalueURI


propertyURIvalueURI


statement

statement


valueURIrdfs:label

“value string”

Vocabulary encoding scheme URI



valueURIrdfs:label

“value string”

Value string

Value string – where property domainis rdfs:Literal


“value string”


valueURIrdfs:label

“value string”^^rdfDatatypeURI

Rich representation


valueURIrdfs:label

“value string”^^syntaxEncodingSchemeURI

Syntax encoding scheme URI


valueURIrdfs:label

“value string”@en

Value string languages


valueURIrdfs:label

“value string”

Related description

propertyURIrdfs:label

“value string”propertyURI


related description

DC RDF Taskforce





Domains and ranges

‘domain’ – the class of resources that a property can be used to describe

‘range’ – the class of resources that are allowed as values of a property

example: what are the domain and range of dc:creator– domain = NonAgentResource– range = Agent

making explicit what has been implicit until now

DC RDF Taskforce





Revising DC definitions

revising the language of the definitions to align them with the DCMI Abstract Model

for example dc:relation– was: A reference to a related resource – change to: A related resource– domain: Resource– range: Resource

also note issue with use of ‘content of the resource’ in definitions

DC RDF Taskforce





Term decision tree

how do you know if something is usable in DC metadata descriptions or not?– has it been explicitly declared as an

element, element refinement or encoding scheme?

– has it been assigned a unique URI?– is the declaration available at that URI?

if the answers are all ‘yes’, then the thing can be used in DC metadata

Workplan for 2006

Workplan - taskforce

develop short document for RDF implementers, clarifying the resource vs. literal string value issue and providing advice on best practice

consider possible RDF encoding changes (in light of above issue), carry out impact analysis and make recommendations

Workplan – tidying up

finalise provision of a persistent URI for the latest version of our XML schemes

finalise revisions to the Guidelines for implementing Dublin Core in XML document

finalise revisions to the Namespace Policy for the Dublin Core Metadata Initiative (DCMI)

Workplan – new stuff

evaluate use of GRDDL as mechanism for transforming arbitrary DC/XML documents into RDF (DCMI AM)

monitor W3C developments for RDF in XHTML and revise current DC/XHTML guidelines as necessary

develop model of ‘application profiles’ representing Box/Period/Point in

DCAM/RDF

DC Architecture WG meeting Monday Sept 12 Slot 1: 15.30 - 17.00 Slot 2: 17.30 - 19.00 Location: Seminar Room 4.1.E01.

Documents

value value representations

encoding dc

dc namespace

value strings

year slide

dcmi namespaces

rich value

dcmi namespace vocabulary