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Transcript of DC Architecture WG meeting Monday Sept 12 Slot 1: 15.30 - 17.00 Slot 2: 17.30 - 19.00 Location:...
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
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
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
resourceURIpropertyURI
valueURIrdfs:label
“value string”
propertyURIvalueURI
rdfs:label“value string”
propertyURIvalueURI
rdf:type vocabularyEncodingSchemeURI
statement
statement
resourceURIpropertyURI
valueURIrdfs:label
“value string”
Vocabulary encoding scheme URI
rdf:type vocabularyEncodingSchemeURI
resourceURIpropertyURI
valueURIrdfs:label
“value string”
Value string
Value string – where property domainis rdfs:Literal
resourceURIpropertyURI
“value string”
resourceURIpropertyURI
valueURIrdfs:label
“value string”^^rdfDatatypeURI
Rich representation
resourceURIpropertyURI
valueURIrdfs:label
“value string”^^syntaxEncodingSchemeURI
Syntax encoding scheme URI
resourceURIpropertyURI
valueURIrdfs:label
“value string”@en
Value string languages
resourceURIpropertyURI
valueURIrdfs:label
“value string”
Related description
propertyURIrdfs:label
“value string”propertyURI
rdfs:label“value string”
related description
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
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
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
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
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
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