dc architecture wg meeting dc-2006, mexico tuesday oct 3 16.30 - 18.30

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


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.


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

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 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

http://dublincore.org/architecturewiki/AMIssues

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).


• 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


• “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


• 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


• 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”



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



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 URIValue string Syntax Enc Scheme URI

Value string Syntax Enc Scheme URI

Resource 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?



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

dc architecture wg meeting dc-2006, mexico tuesday oct 3 16.30 - 18.30

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