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An abstract model for DCMI metadata descriptions Andy Powell UKOLN, University of Bath, UK UKOLN is supported.

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Presentation on theme: "An abstract model for DCMI metadata descriptions Andy Powell UKOLN, University of Bath, UK UKOLN is supported."— Presentation transcript:

1 An abstract model for DCMI metadata descriptions Andy Powell a.powell@ukoln.ac.uk UKOLN, University of Bath, UK http://www.ukoln.ac.uk/ UKOLN is supported by: DC Usage Board meeting at DC2003, Seattle September/October 2003

2 DC-2003 - Seattle, Sept/Oct 2003 2 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

3 DC-2003 - Seattle, Sept/Oct 2003 3 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?

4 DC-2003 - Seattle, Sept/Oct 2003 4 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

5 DC-2003 - Seattle, Sept/Oct 2003 5 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

6 DC-2003 - Seattle, Sept/Oct 2003 6 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?

7 DC-2003 - Seattle, Sept/Oct 2003 7 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

8 DC-2003 - Seattle, Sept/Oct 2003 8 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…

9 DC-2003 - Seattle, Sept/Oct 2003 9 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

10 DC-2003 - Seattle, Sept/Oct 2003 10 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

11 DC-2003 - Seattle, Sept/Oct 2003 11 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??

12 DC-2003 - Seattle, Sept/Oct 2003 12 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!

13 DC-2003 - Seattle, Sept/Oct 2003 13 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

14 DC-2003 - Seattle, Sept/Oct 2003 14 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

15 DC-2003 - Seattle, Sept/Oct 2003 15 …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)

16 DC-2003 - Seattle, Sept/Oct 2003 16 …or to put it differently simple DC is an ‘application profile’ that only uses terms taken from the DCMES

17 DC-2003 - Seattle, Sept/Oct 2003 17 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

18 DC-2003 - Seattle, Sept/Oct 2003 18 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

19 DC-2003 - Seattle, Sept/Oct 2003 19 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

20 DC-2003 - Seattle, Sept/Oct 2003 20 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

21 DC-2003 - Seattle, Sept/Oct 2003 21 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)

22 DC-2003 - Seattle, Sept/Oct 2003 22 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

23 DC-2003 - Seattle, Sept/Oct 2003 23 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

24 DC-2003 - Seattle, Sept/Oct 2003 24

25 DC-2003 - Seattle, Sept/Oct 2003 25 Example 1 – dc:creator Andy Powell a.powell@ukoln.ac.uk Example RDF description using dc:creator…

26 DC-2003 - Seattle, Sept/Oct 2003 26 Andy Powell a.powell@ukoln.ac.uk Example 1 – 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

27 DC-2003 - Seattle, Sept/Oct 2003 27 Andy Powell a.powell@ukoln.ac.uk Example 1 – dc:creator dc:creator Andy Powell… my:affiliation a.powell@uko… 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

28 DC-2003 - Seattle, Sept/Oct 2003 28 Andy Powell Example 1 – dc:creator dc:creator Andy Powell… rdfs:label Andy Powell a.powell@ukoln.ac.uk my:affiliation a.powell@uko… 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…

29 DC-2003 - Seattle, Sept/Oct 2003 29 Andy Powell Example 1 – dc:creator valueURI dc:creator Andy Powell… rdfs:label Andy Powell a.powell@ukoln.ac.uk valueURI my:affiliation a.powell@uko… 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…

30 DC-2003 - Seattle, Sept/Oct 2003 30 Andy Powell Example 1 – dc:creator valueURI dc:creator Andy Powell… rdfs:label Andy Powell a.powell@ukoln.ac.uk valueURI my:affiliation a.powell@uko… 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

31 DC-2003 - Seattle, Sept/Oct 2003 31 Andy Powell a.powell@ukoln.ac.uk Example 1 – dc:creator valueURI dc:creator Andy Powell… rdfs:label Andy Powell a.powell@ukoln.ac.uk valueURI my:affiliation a.powell@uko… my:email UKOLN, Univ… a.powell@uko… Andy Po… my:name relatedMetadataURI rdfs:seeAlso Use rdf:seeAlso to form linkage between description and relatedMetadata…

32 DC-2003 - Seattle, Sept/Oct 2003 32 Example 2 – dc:subject D08.586.682.075.400 Formate Dehydrogenase Example RDF description using dc:subject (taken from Qualified DC in RDF recommendation…

33 DC-2003 - Seattle, Sept/Oct 2003 33 Example 2 – dc:subject D08.586.682.075.400 Formate Dehydrogenase dcterms:MESH dc:subject rdf:type D08.586… rdf:type rdfs:label Formated… rdfs:value …and the RDF model it represents.

34 DC-2003 - Seattle, Sept/Oct 2003 34 Example 2 – dc:subject D08.586.682.075.400 Formate Dehydrogenase dcterms:MESH dc:subject rdf: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

35 DC-2003 - Seattle, Sept/Oct 2003 35 Example 2 – dc:subject D08.586.682.075.400 dcterms:MESH dc:subject rdf:type D08.586.682.075.400 Formate Dehydrogenase 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…

36 DC-2003 - Seattle, Sept/Oct 2003 36 Example 2 – dc:subject D08.586.682.075.400 valueURI dcterms:MESH dc:subject rdf:type D08.586.682.075.400 Formate Dehydrogenase 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…

37 DC-2003 - Seattle, Sept/Oct 2003 37 Example 2 – dc:subject D08.586.682.075.400 valueURI dcterms:MESH dc:subject rdf:type D08.586.682.075.400 Formate Dehydrogenase 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…

38 DC-2003 - Seattle, Sept/Oct 2003 38 Example 2 – dc:subject D08.586.682.075.400 valueURI dcterms:MESH dc:subject rdf:type D08.586.682.075.400 Formate Dehydrogenase valueURI dcterms:MESH D08.586… Formated… relatedMetadataURI rdfs:seeAlso Use rdf:seeAlso to form linkage between description and relatedMetadata… rdfs:label Formated…

39 DC-2003 - Seattle, Sept/Oct 2003 39 Abstract DC model D08.586.682.075.400 valueURI dcterms:MESH dc:subject rdf:type D08.586.682.075.400 Formate Dehydrogenase 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)


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