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Schemas or Vocabularies?

Schemas or Vocabularies?. April 26, 2005 OASIS Symposium on the Future of XML Vocabularies Bob DuCharme LexisNexis. Outline. review Dublin Core “vocabularies” creating vocabularies (and maybe schemas): required and optional steps case study: PRISM. Dublin Core.

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Schemas or Vocabularies?

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  1. Schemas or Vocabularies? April 26, 2005 OASIS Symposium on the Future of XML Vocabularies Bob DuCharme LexisNexis 1

  2. Outline • review Dublin Core • “vocabularies” • creating vocabularies (and maybe schemas): required and optional steps • case study: PRISM 2

  3. Dublin Core • Dublin Core Metadata Initiative • dublincore.org • DCMI Metadata Terms: elements, element refinements, encoding schemes, and vocabulary terms • element: “A discrete unit of data or metadata. An element may contain subelements that are called qualifiers in Dublin Core. ” • creator, date, description, format, identifier… 3

  4. “vocabulary”? • list of words? • DTD? • schema? • W3C Schema? • RELAX NG schema? • RDF Schema? 4

  5. Mandatory step 1 Define your standard list of words: • The actual words to use (PublishDate? publish-date? PubDate?) • Their meanings. • (optional) Value restrictions, e.g. • formatting, such as ISO 8601 for dates (“2005-04-26T09:20”) • list of values to choose from (Y/N, True/False, ISO 3166 country codes) 5

  6. Example Dublin Core definition 6

  7. Optional Steps 2 and 3 • Figure out the relationships of your labeled pieces of information • Write it down in a machine-readable form 7

  8. RDF Schemas “RDF user communities also need the ability to define the vocabularies (terms) they intend to use in those statements, specifically, to indicate that they are describing specific kinds or classes of resources, and will use specific properties in describing those resources…” - W3C RDF Tutorial 8

  9. Validation? “RDF classes and properties are in some respects very different from programming language types. RDF class and property descriptions do not create a straightjacket into which information must be forced, but instead provide additional information about the RDF resources they describe.” 9

  10. Flexibility • advantage: more systems can adapt, politically easier to sell • disadvantage: fuzziness, more work to adopt a standard 10

  11. PRISM • Publishing Requirements for Industry Standard Metadata • “Developing a standard XML metadata vocabulary for the publishing industry” • http://www.prismstandard.org • v 1.0: 2001; current version: 1.2 11

  12. PRISM 1. 2 “elements” 12

  13. PRISM DTDs • metadata vs. data: • article titles, bylines • identifying inline entities • PRISM Aggregator DTD (PAM) • Two levels of compliance • level one: well-formed XML, dc:identifier • level two: RDF profile, rdf:about 13

  14. PRISM RDF Schema • Tony Hammond, Nature Publishing Group • under “contributed resources” on PRISM website 14

  15. Lessons Learned • Which works best for your industry: vocabulary, DTD, XSD, RNG… • Layered approach a good option • Say what you mean 15

  16. Schemas or Vocabularies? April 26, 2005 OASIS Symposium on the Future of XML Vocabularies Bob DuCharme LexisNexis 16

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