dc architecture wg meeting dc-2006, mexico tuesday oct 3 16.30 - 18.30
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DC Architecture WG meeting
DC-2006, MexicoTuesday Oct 316.30 - 18.30
Agenda
introductory session– where we’ve been and where we are
going– but not a tutorial
5 minute break advanced session
– meeting of the working group– detailed discussion about DC Abstract
Model, DC-RDF, DC-XML
Aims
knowledge sharing
discussion of issues– do the proposed revisions to abstract model
address concerns that have been raised– relationship between DCAM and SKOS– consider nature of our DC-XML guidelines
intention is to inform the next iteration of the working drafts
Important
this meeting is intended to be informal and interactive
please ask questions if you don’t understand
please raise issues if you disagree introduce yourself before speaking
Session leaders
Andy Powell– chair of DC Architecture / DC Abstract
Model
Pete Johnston– author of DC-XML / DC Abstract Model
Mikael Nilsson– author of DC-RDF / DC Abstract Model
Tom Baker– chair of DC Usage Board
Agenda
review of progress during the year– summary of DCMI Abstract Model,
DC-RDF and DC-XML– note about related Usage Board
activities
DC-Architecture and Usage Board roadmap for next year
Progress - DC-XML
Guidelines for implementing Dublin Core in XML – DCMI Recommendation, April 2003
pre-dates development of DCAM uses two earlier, simpler “abstract
models”– “Simple DC” model can be mapped to DCAM
description model– “Qualified” model can not be mapped to
DCAM description model
DC-XML (2)
no DCMI guidance for representing DC description sets using XML
March 2006: DCMI contract to produce revised XML format
working draft issued for comment comments currently being
addressed
Progress DC-RDF
The Knowledge Management Research Group 11
DC-Architecture WGDC-RDF updates
Mikael [email protected]
The Knowledge Management Research GroupRoyal Institute of Technology, Stockholm
http://kmr.nada.kth.se
The Knowledge Management Research Group 12
New DC-RDF Working Draft!
Successful public comment in June, 2006 Will be revised and discussed more If accepted, will replace
Expressing Simple Dublin Core in RDF/XML, a DCMI Recommendation from July 2002;
Expressing Qualified Dublin Core in RDF / XML, a DCMI Proposed Recommendation from May 2002.
The Knowledge Management Research Group 13
Main features
a unified specification for Dublin Core in RDF full support for the DCMI Abstract Model good integration with other RDF metadata supports domains and ranges
<http://www.example.com> dcterms:creator "John Smith" – no longer valid!
much more regular – many complicated options deprecated
The Knowledge Management Research Group 14
Progress - Abstract Model
DCMI Abstract Model has generated comments from:– DCMI Usage Board– DCMI Working Groups, particularly WGs developing
DCAPs– implementers of DCAPs– developers/implementers of related specs (e.g.
SKOS)– researchers– implementers of metadata registries– authors/editors of “encoding guidelines”
specifications– …
Abstract Model (2)
use of DCAM has:– highlighted omissions, ambiguities,
redundancies, errors– created better understanding of what is
required– emphasised value of an abstract model!
all of which has fed into process for producing draft revised abstract model (see Wiki)– http://dublincore.org/architecturewiki/AMDraftUpdate
Progress - Namespace Policy
no real progress! revised and discussed at DC-Arch
meeting last year pretty much static since then may be some minor issues around
replicating terms from DC namespace to DCTERMS namespace
need to move to recommendation
Usage Board activities
in parallel the DC Usage Board has been working on assigning domains and
ranges to DCTERMS– in order to make some of the property
semantics explicit in machine-readable form
clarifying whether each of the current encoding schemes is a ‘syntax encoding scheme’ or a ‘vocabulary encoding scheme’
Liaison with Swoogle
before assigning domains and ranges we needed to understand how DC properties are currently used in RDF
obtained statistics from Swoogle– e.g. showed that dc:creator mainly used
with range of rdfs:Literal
as a result, our current plan is to copy the 15 DCMES properties into the DCTERMS namespace and assign domains and ranges to them there
DC Arch and Usage Board Roadmap for next year
Tom
Usage Board support forDC Architecture developments
• September 2006 – Manzanillo– DC-Architecture
• DCAM update• Revised DC-RDF, DC-XML, DC-Text
– Usage Board• DCMES changes – finalization• Range vocabulary – review definitions, proposed
assignments• Existing terms as syntax or vocabulary encoding
schemes
Usage Board and DC-Architecture:
Joint Work Plan
• October through December 2006– DC-Architecture
• Prepare DCAM, DC-Text, DC-XML, DC-RDF, DCMI Namespace Policy for public comment
– Extend DCAM with Vocabulary Model and Profile Model
• RDF schemas with ranges for purposes of testing
– UB• Prepare range vocabulary for public comment
Usage Board and DC-Architecture:
Joint Work Plan• January to March 2007 – DCMI
– Public comment period for DCAM, etc• Resulting in DCMI Recommendations
– User-oriented “how-to” documentation for making profiles and vocabularies
• April 2007 – Usage Board– Approve vocabulary range as new DCMI
terms– Approve assignment of ranges to existing
terms
5 minute break
Agenda
Abstract Model DC-RDF DC-XML
DCMI Abstract Model
Pete
Pete Johnston, Eduserv [email protected]
www.eduserv.org.uk/foundation
DCMI Abstract Model: issues and proposed changesDCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico
Background
• DCMI Abstract Model– DCMI Recommendation March 2005
• DCAM describes– Components and constructs that make up an
information structure (“DC description set”)
– How that information structure is to be interpreted
• DCAM does not describe how to represent DC description set in concrete form
DCAM Description Model
• a description set is made up of one or more descriptions • a description is made up of
– zero or one resource URI and – one or more statements
• a statement is made up of – exactly one property URI and – zero or one reference to a value in the form of a value URI – zero or more representations of a value, each in the form of a value
representation – zero or one vocabulary encoding scheme URI
• a value representation is either – a value string or – a rich representation
• a value string may have an associated value string language • a value string may have an associated syntax encoding scheme URI • a value may be the subject of a related description
Resource URI
Property URI Rich representation
Property URI Value URI Vocab Enc Scheme URI
Property URIValue string Syntax Enc Scheme URI
Value string Syntax Enc Scheme URI
Resource URI
Property URI Rich representation
Property URI Value URI Vocab Enc Scheme URI
Property URI Value string Syntax Enc Scheme URI
Statement
Description
Description Set
DCMI Abstract Model in use
• Use of DCAM has generated comments from e.g.– DCMI Usage Board– DCMI Working Groups, particularly WGs developing DCAPs– Implementers of DCAPs– Developers/implementers of related specs (e.g. SKOS)– Researchers– Implementers of metadata registries– Authors/editors of “encoding guidelines” specifications– (and others!)
• Use of DCAM has – highlighted omissions, ambiguities, redundancies, errors– created better understanding of what is required– emphasised value of an abstract model!
Proposed changes
• Issues collated in• http://dublincore.org/architecturewiki/AMIssues
1. Some editorial/presentational change
2. Remove some historical information
3. Clarify existing concepts/constructs
4. Extend to include new concepts/constructs
Editorial/presentational change
• Purpose of DCAM– (Current) “The primary purpose of this document is to provide a
reference model against which particular DC encoding guidelines can be compared. To function well, a reference model needs to be independent of any particular encoding syntax. ”
– Doesn’t reflect role of DCAM in defining what DC metadata is, the nature of the components used, and how they are interpreted
– Also DCAM should be starting point for “encoding guidelines”– (Proposed) “The primary purpose of this document is to specify
the components and constructs used in Dublin Core metadata. It defines the nature of the components used and describes how those components are combined to create information structures. It provides a reference model which is independent of any particular encoding syntax.”
Editorial/presentational change
• Vocabulary Model– Description of types of terms and types of
relationships that exist between terms
– Based on RDF Schema
– Currently embedded in “Resource Model”/Figure 1
– Useful to make more explicit
– Also some extensions required (more later)
Remove some historical information
• Appendices contain discussion of specs based on earlier/different “abstract models”– e.g. appendices on encoding guidelines in 2003
– attempts to retrofit DCAM confusing (inaccurate?)
– redundant once DCMI adopts encoding guidelines based on DCAM
• Confused terminology in discussion of “structured values”– addressed in revisions to DCSV, Box, Period, Point
(2006)
• Useful for context of DCAM in 2003, but should not be part of document
Clarify existing concepts/constructs
• Phrasing of some definitions is inconsistent with usage in text e.g.– Term
• (Current) The generic name for a property (i.e. element or element refinement), vocabulary encoding scheme, syntax encoding scheme or concept taken from a controlled vocabulary (concept space).
• (Proposed) A property (i.e. element or element refinement), vocabulary encoding scheme, syntax encoding scheme or concept taken from a controlled vocabulary (concept space).
Clarify existing concepts/constructs
• Sub-property/Sub-class– Currently modelled as distinct classes
– Should be represented in Vocabulary Model as relationships between properties, classes
– i.e. same concepts as in RDF Schema
– Also provide definitions in glossary
Clarify existing concepts/constructs
• “Description Set”– Need to emphasise that “description set” is primary
“abstract information structure”– Proposal: Add “A description set is a set of one or more
descriptions” to textual description of description model • “Related description”
– Need to emphasise that a “related description” is just a description
– Proposal: use “description of value” etc • “Resource”/”Resource URI” and “Value”/”Value URI”
– A value is a resource, so sometimes use of “resource” seems ambiguous
– Proposal: use “described resource” to refer to subject of description
Clarify existing concepts/constructs
• Value strings, language tags & syntax encoding schemes– (Currently) allow value string to be associated with both
a language tag and a syntax encoding scheme (datatype)
– Proposal: permit value string to be associated with either language tag or syntax encoding scheme, or neither, but not both
• “Empty statements”– (Currently) allow a statement with no value URI or value
representation and no (“related”) description of value– Proposal: specify that value URI or value representation
must be provided unless value is subject of separate description
Clarify existing concepts/constructs
• Syntax encoding schemes– (Currently) A syntax encoding scheme indicates that the value
string is formatted in accordance with a formal notation, such as "2000-01-01" as the standard expression of a date.
– SES includes a “contract” for interpretation of literal– But “formatted” too narrow
• ISO 3166, xsd:Boolean, xsd:int
– Doesn’t capture notion that SES indicates that literal “stands for” something else
– Proposal: A syntax encoding scheme is a set of strings that is associated with a set of rules which describe a mapping between that set of strings and a set of resources. The mapping rules may be based on a description of how the string is structured (e.g. DCMI Box) or they may be based on a simple enumeration of all the strings and the corresponding resource (e.g. ISO 3166).
Extend to include new concepts/constructs
• Range/domain– DCMI plans to make range/domain assertions for
DCMI-owned properties• Making explicit to software what is implicit in
human-readable descriptions
– Should be added to Vocabulary Model as relationships between properties, classes
– i.e. same concepts as in RDF Schema
– Also provide definitions in glossary
Extend to include new concepts/constructs
• Vocabulary Encoding Scheme v Class of Value– (currently) VES = class of Value– Conflict with existing DCMI use of concept e.g.
• class of LCSH terms considered a VES• class of collections or class of persons not considered VES
– Also integration with SKOS• relation between Concept and ConceptScheme is
skos:inScheme not rdf:type (instance-of)• so difficult to use same resource as skos:ConceptScheme
and as VES– What distinguishes a VES from a Class?– Proposal: VES as enumerable set of resources– Proposal: Add Value Class URI to description model (in
addition to VES URI)
Other issues not yet discussed
• Rich Representations & MIME types– Should DCAM description model specify that rich
representation should be associated with MIME type?
• “Conformance to DCAM”
Pete Johnston, Eduserv [email protected]
www.eduserv.org.uk/foundation
DCMI Abstract Model: issues and proposed changesDCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico
Encoding guidelinesDC-RDF
Mikael
Encoding guidelinesDC-XML
Pete
Pete Johnston, Eduserv [email protected]
www.eduserv.org.uk/foundation
Expressing DC metadata in XML: a status report to DCMI Architecture WG DCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico
Expressing DC metadata in XML
• Background• DC-XML 2006-05-29
– public comment version • DC-XML 2006-07-04
– draft to DC Arch WG– verbosity, human readability, “hard to explain”– no “term-level” validation with W3C XML Schema
• DC-XML-Full 2006-09-18 – draft to DC Arch WG– extension to DC-XML 2006-07-04
• DC-XML-Min 2006-09-18 – draft to DC Arch WG– supports subset of DCAM description model
• Moving forward?
Background
• DCMI Abstract Model– DCMI Recommendation March 2005
• DCAM describes– Components and constructs that make up an
information structure (“DC description set”)
– How that information structure is to be interpreted
• DCAM does not describe how to represent DC description set in concrete form
Resource URI
Property URI Rich representation
Property URI Value URI Vocab Enc Scheme URI
Property URIValue string Syntax Enc Scheme URI
Value string Syntax Enc Scheme URI
Resource URI
Property URI Rich representation
Property URI Value URI Vocab Enc Scheme URI
Property URI Value string Syntax Enc Scheme URI
Statement
Description
Description Set
Background
• Guidelines for implementing Dublin Core in XML – DCMI Recommendation, April 2003 – Pre-dates development of DCAM– Uses two earlier, simpler “DC abstract models”– “Simple DC metadata record” model can be mapped to
DCAM description model– “Qualified DC metadata record” model can not be
mapped to DCAM description model
• No DCMI guidance for representing DC description sets using XML
• March 2006: DCMI contract to produce revised XML format
Design Principles
• Should support all features of DCAM description model
• Not required to express DCAM vocabulary model (subproperty, subclass etc)
• Should be easily usable with XPath, XPointer, XQuery etc
• Should not be dependent on features of one XML Schema language
• Should be amenable to description using W3C XML Schema
• But not required that all constraints of a DCAP captured in W3C XML Schema
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dc:title> <dcx:valueString>DCMI Home Page</dcx:valueString> </dc:title> <dc:subject dcx:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dc:subject> <dcterms:isPartOf dcx:valueURI="http://dublincore.org/site" /> <dc:publisher dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <my:name> <dcx:valueString>Dublin Core Metadata Initiative</dcx:valueString> </my:name> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-05-29
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dc:title> <dcx:valueString>DCMI Home Page</dcx:valueString> </dc:title> <dc:subject dcx:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dc:subject> <dcterms:isPartOf dcx:valueURI="http://dublincore.org/site" /> <dc:publisher dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <my:name> <dcx:valueString>Dublin Core Metadata Initiative</dcx:valueString> </my:name> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-05-29
Property URI as XML QName (as XML element name)
VES URI as XML attribute value
Resource URI, Value URI as XML attribute values
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dc:title> <dcx:valueString>DCMI Home Page</dcx:valueString> </dc:title> <dc:subject dcx:vocabEncSchemeQName="dcterms:LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dc:subject> <dcterms:isPartOf dcx:valueURI="http://dublincore.org/site" /> <dc:publisher dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <my:name> <dcx:valueString>Dublin Core Metadata Initiative</dcx:valueString> </my:name> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-05-29
VES URI as XML QName (as XML attribute value)
(“Related”) description of value linked by id/idref
Main comments on DC-XML 2006-05-29
• XML elements v XML attributes
• Variation in representation of URIs– Resource URI, Value URI as URI
– VES URI, SES URI as URI or as QName
– Property URI as QName
• XML QNames in XML attribute values
• DCAM issues– Rich representations and MIME types
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/title"> <dcx:valueString>DCMI Home Page</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/subject" dcx:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyURI="http://purl.org/dc/terms/isPartOf" dcx:valueURI="http://dublincore.org/site" /> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/publisher" dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <dcx:statement dcx:propertyURI="http://my.example.org/terms/name"> <dcx:valueString>Dublin Core Metadata Initiative</dcx:valueString> </dcx:statement> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-07-04
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/title"> <dcx:valueString>DCMI Home Page</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/subject" dcx:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyURI="http://purl.org/dc/terms/isPartOf" dcx:valueURI="http://dublincore.org/site" /> <dcx:statement dcx:propertyURI="http://purl.org/dc/elements/1.1/publisher" dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <dcx:statement dcx:propertyURI="http://my.example.org/terms/name"> <dcx:valueString>Dublin Core Metadata Initiative</dcx:valueString> </dcx:statement> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-07-04
Property URI as XML attribute value
Statement Element name = dcx:statement
<dcx:descriptionSet> <dcx:namespaceDeclaration dcx:prefix="dc" dcx:namespaceURI="http://purl.org/dc/elements/1.1/" /> <dcx:namespaceDeclaration dcx:prefix="dcterms" dcx:namespaceURI="http://purl.org/dc/terms/" /> <dcx:namespaceDeclaration dcx:prefix=“page" dcx:namespaceURI="http://dublincore.org/pages/" /> <dcx:description dcx:resourceQualName="page-home"> <dcx:statement dcx:propertyQualName=“dc-title"> <dcx:valueString>DCMI Home Page</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyQualName=“dc-subject" dcx:vocabEncSchemeQualName="dcterms-LCSH"> <dcx:valueString>Metadata</dcx:valueString> </dcx:statement> <dcx:statement dcx:propertyQualName="dcterms-isPartOf" dcx:valueURI="http://dublincore.org/site" /> </dcx:description> </dcx:descriptionSet>
DC-XML 2006-07-04
Qualified Name not based on XML QNames
Main comments on DC-XML 2006-07-04
• XML element names reflect names of DCAM constructs – cf TriX for RDF
• Verbose• Limits validation that can be performed using W3C XML
Schema? (e.g. “property-level validation”)• Difficult to explain to human reader/writer?
– Q: “Why can’t I just use this?”<dcx:descriptionSet> <dcx:description> <dc:subject>Metadata</dc:subject> </dcx:description></dcx:descriptionSet>
– A: (Because XML element represents statement and DCAM supports multiple value strings per statement)
• But if we agree on a subset of the DCAM model….
DCAM Description Model (Subset)
• a description set is made up of one or more descriptions • a description is made up of
– zero or one resource URI and – one or more statements
• a statement is made up of – exactly one property URI and – zero or one reference to a value in the form of a value URI – zero or one representation of a value in the form of a
value string – zero or one vocabulary encoding scheme URI – zero or one value class URI
• a value string may be associated with either a value string language or a syntax encoding scheme URI
• a value may be the described resource of another description in the description set
<dcx:descriptionSet> <dcx:description dcx:resourceURI="http://dublincore.org/pages/home"> <dc:title>DCMI Home Page</dc:title> <dc:subject dcx:vocabEncSchemeURI="http://purl.org/dc/terms/LCSH"> Metadata </dc:subject> <dcterms:isPartOf dcx:valueURI="http://dublincore.org/site" /> <dc:publisher dcx:descriptionRef="dcmi" /> </dcx:description> <dcx:description dcx:descriptionId="dcmi"> <my:name>Dublin Core Metadata Initiative</my:name> </dcx:description> </dcx:descriptionSet>
DC-XML-Min 2006-09-18
Main comments on DC-XML-Min 2006-09-18
• Addresses problems of verbosity• Could DC-XML-Min be made a (W3C XML-Schema-
friendly) profile of RDF/XML?– dcxm:description -> rdf:Description– @dcxm:resourceURI -> @rdf:about– @dcxm:valueURI -> @rdf:resource– @dcxm:vocabEncSchemeURI -> @dcrdf:inScheme or
@dcrdf:isMemberOf (or whatever we decide the property for that relationship is)
– @dcxm:valueClassURI -> @rdf:type– @dcxm:descriptionId -> @rdf:nodeID– @dcxm:descriptionRef -> @rdf:nodeID
<dcx:descriptionSet> <dcx:description rdf:about="http://dublincore.org/pages/home"> <dc:title>DCMI Home Page</dc:title> <dc:subject dcrdf:isMemberOf="http://purl.org/dc/terms/LCSH"> Metadata </dc:subject> <dcterms:isPartOf rdf:resource="http://dublincore.org/site" /> <dc:publisher rdf:nodeID="dcmi" /> </dcx:description> <dcx:description rdf:nodeID ="dcmi"> <my:name>Dublin Core Metadata Initiative</my:name> </dcx:description> </dcx:descriptionSet>
Main comments on DC-XML-Min 2006-09-18
• However… need blank nodes and typed literalsProperty Element with @rdf:parseType=“Resource” and child Property Element:
<rdf:Description rdf:about="http://dublincore.org/pages/home"> <dc:subject rdf:parseType="Resource"> <dcrdf:valueString>History</dcrdf:valueString> </dc:subject></rdf:Description>
Node Elements and rdf:nodeID:
<rdf:Description rdf:about="http://dublincore.org/pages/home"> <dc:subject rdf:nodeID="history" /></rdf:Description><rdf:Description rdf:nodeID="history"> <dcrdf:valueString>History</dcrdf:valueString></rdf:Description>
Moving forward?
• DC-XML-Full 2006-09-18– Supports full DCAM description model (incl. Value Class)– Uses dcx:statement for Statement Element name– All URIs as attribute values– No XML QNames in XML content (but DC Qualified Name
mechanism needs testing)• DC-XML-Min 2006-09-18
– Supports subset of DCAM description model– Property URIs as XML QNames (XML element names); other URIs
as attribute values– Probably not a profile of RDF/XML – but we do have GRDDL!
• Does DCMI need both?• Or is DC-XML-Min sufficient?
Pete Johnston, Eduserv [email protected]
www.eduserv.org.uk/foundation
Expressing DC metadata in XML: a status report to DCMI Architecture WG DCMI Architecture Working Group DC-2006: Metadata for Knowledge & Learning, Manzanillo, Mexico
Workplan for next year
Andy