The Dublin Core Abstract Model

1
The Dublin Core Abstract Model a packaging
standard?

• Content Packaging for Complex Objects Technical
  Workshop

flickr photo by amalthya
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Why Dublin Core?
this workshop is about content packaging not
metadata!?

• well maybe

DC doesnt do content packaging does it?
DC is just 15 elements for describing Web pages
isnt it?
3
DC and content packaging
http//dublincore.org/documents/abstract-model/

• this talk is about the DCMI Abstract Model
• and its relationship to content packaging
• it is not intended as a tutorial
• but I appreciate that the DCMI Abstract Model is
  new to many of you
• I will therefore start by summarising the
  background, context and main features of the DCAM
• then Ill give some examples
• and finally try to draw some conclusions

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DCMI Abstract Model background

• in the early days of Dublin Core there was no
  explicit model associated with DC metadata
  descriptions
• there were implicit models and conventional
  wisdom
• largely flat in nature i.e. a set of metadata
  elements describing a single thing (e.g. a Web
  page)
• and there were known problems
• like sometimes it was obvious that an element was
  really being used to describe a second thing
  (e.g. the author of a Web page)

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DCMI Abstract Model background

• as the various DC syntaxes matured
• XHTML, XML and RDF/XML
• the underlying model became more important
• primarily as a mechanism for mapping between
  syntaxes
• and there have been a number of attempts at
  applying the RDF model to DC

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DCMI Abstract Model key features

• the DCAM (first published in 2005) attempts to
  make explicit the model that underpins DC
• the DCAM starts from the central notion of a
  description set
• a set of descriptions about a group of related
  things (resources)
• where each description is about a single
  resource
• and where each description is essentially made
  up of property/value pair statements
• descriptions sets are instantiated as records
  (e.g. using XHTML, XML or RDF/XML) for the
  purpose of exchanging information between
  networked systems

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Model summary
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DCAM and relationships

• the DCAM is very open about the nature of the
  relationships between the resources described in
  a description set
• whole / part (e.g. book / chapter / section /
  page)
• physical / digital (painting / digitised
  painting)
• object / human (document / author)
• conceptual / physical (work / item)
• or all of the above!
• the relationships between things is articulated
  in an application model and captured using the
  properties specified in an application profile

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Example 1 Book application model

• here is a very simple application model

0..8
hasPart
Book
Chapter
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Example 1 pseudo-XML description set

• ltdescriptionSetgt
• ltdescription resourceURIhttp//example.org/mybo
  okgt
• ltstatement propertyURIdctermshasPart
  valueURIhttp//example.org/chapter1 /gt
• ltstatement propertyURIdctermshasPart
  valueURIhttp//example.org/chapter2 /gt
• lt/descriptiongt
• ltdescription resourceURIhttp//example.org/chap
  ter1gt
• ltstatement propertyURIdctitlegt
• ltvalueStringgtChapter 1lt/valueStringgt
• lt/statementgt
• lt/descriptiongt
• ltdescription resourceURIhttp//example.org/chap
  ter2gt
• ltstatement propertyURIdctitlegt
• ltvalueStringgtChapter 2lt/valueStringgt
• lt/statementgt
• lt/descriptiongt
• lt/descriptionSetgt

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Note 1 objects packaged by reference

• note that objects within the package (the
  resources described within the description set)
  are passed by reference
• i.e. their URL is provided
• this is in common with other packaging standards
• passing by value (i.e. embedding the object
  in-line) is theoretically possible using the DCAM
  rich representation mechanism (but this is not
  discussed further here)

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Note 2 - ordering

• the DCAM has no built-in support for ordering
• the model is graph-based rather than being an
  ordered tree
• for applications requiring ordering, e.g. the
  chapters in a book, it would therefore be
  necessary to invent properties (e.g.
  mysequenceNumber) to capture the ordering as
  part of the description

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Eprints application model
http//www.ariadne.ac.uk/issue50/allinson-et-al/

• here is a more complex application model

ScholarlyWork
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Example 2 psuedo-XML

• ltdescriptionSetgt
• ltdescription resourceURIhttp//eprints.gla.ac.u
  k/503/gt
• ltstatement propertyURIdctitlegt
  ltvalueStringgtAttempts to detect
  retrotransposition and de novo deletion of Alus
  and other dispersed repeats at specific loci in
  the human genome lt/valueStringgt lt/statementgt
• ltstatement propertyURIeprintisExpressedAs
  valueRefexpression1 /gt
• lt/descriptiongt
• ltdescription resourceIdexpression1 gt
• ltstatement propertyURIeprintisManifestedAs
  valueRefpdfmanifestation /gt
• lt/descriptiongt
• ltdescription resourceIdpdfmanifestation gt
• ltstatement propertyURIeprintisAvailableAs
• valueURIhttp//eprints.gla.ac.uk/503/01/Eu_
  J._Hum_Gen.9(2)143_.pdf /gt
• ltstatement propertyURIeprintisAvailableAs
• valueURIhttp//www.nature.com/ejhg/journal/
  v9/n2/pdf/5200590a.pdf /gt
• ltdescriptiongt
• lt! descriptions of the two copies here --gt
• lt/descriptionSetgt

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Note 3 - Compound vs. complex objects

• note that the relationships between objects in
  this example are more complex than hasPart or
  isPartOf
• because the model doesnt just deal with digital
  objects
• it may be worth drawing a distinction between
• compound objects (where objects have whole /
  part type structural relationships) and
• complex objects (where there are arbitrary
  relationships between objects) ??
• most objects in digital libraries are complex
  not just compound

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Summary why DC?

• DC (and the DCAM) provides a simple packaging
  framework
• where objects within the package are typically
  passed by reference
• highly flexible and extensible relationship
  framework between objects
• supports multiple syntax encodings
• compatible with Semantic Web (which allows for
  possibility of inferencing across complex objects
  from unknown sources)
• content packaging is largely about relationships
  i.e. it is just metadata

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Questions