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

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

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…

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

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 (“ T09:20”) –list of values to choose from (Y/N, True/False, ISO 3166 country codes)

6 Example Dublin Core definition Term Name: format URI: Label:Format Definition:The physical or digital manifestation of the resource. Comment: Typically, Format may include the media-type or dimensions of the resource. Format may be used to determine the software, hardware or other equipment needed to display or operate the resource. Examples of dimensions include size and duration. Recommended best practice is to select a value from a controlled vocabulary (for example, the list of Internet Media Types [MIME] defining computer media formats). Reference: [MIME] Type of Term:element Status:recommended Date Issued:

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

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

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.”

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

11 PRISM Publishing Requirements for Industry Standard Metadata “Developing a standard XML metadata vocabulary for the publishing industry” v 1.0: 2001; current version: 1.2

12 PRISM 1. 2 “elements” General Purpose ProvenanceDates and TimeSubject Description RelationsRightsControlled Vocabs Inline Markup dc: identifier title creator contributor description language format type prism: category dc: publisher source prism: distributor edition issn issueName number startingPage Volume prism: creationDate expirationDate modificationDate publicationDate releaseDate receptionDate dc: coverage subject prism: event industry location person organization section prism: isCorrectionOf hasCorrection isPartOf hasPart isVersionOf hasVersion isFormatOf hasFormat References isReferencedBy isBasedOn isBasisFor isTranslationOf hasTranslation requires isRequiredBy isAlternativeFor hasAlternative dc: rights prism: copyright expirationTime releaseTime rightsAgent prl: geography industry usage pcv: broaderTerm code definition Descriptor label narrowerTerm relatedTerm synonym Vocabulary pim: event industry location objectTitle organization person quote

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

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

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

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