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Statements about statements -- Help needed!

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  • Misha Wolf
    In working on the XSLT transform to convert NewsML 2 [1] metadata to RDF, we re having problems with statements about statements. We would appreciate advice,
    Message 1 of 2 , Dec 22, 2005
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      In working on the XSLT transform to convert NewsML 2 [1] metadata
      to RDF, we're having problems with statements about statements. We
      would appreciate advice, especially if it is couched in terms we can
      understand.

      A NewsML metadata element can take as a value one of the following:

      - a concept, represented by a CURIE [2]

      - a string

      - a structured element, eg one describing a person or an
      organisation

      - an rdf:bag containing elements whose values are taken from the
      above list

      The metadata element typicaly relates the value to a news item, eg:

      - a creator|contributor|subject|genre|etc of news item X is Y

      NewsML 2 allows one to make a number of additional statements. Some
      of these are about the value itself; others are about the assignment
      of the value.

      The first category hasn't caused us problems. Examples of such
      statements are:

      - concept X is of type Y

      - concept X is the same concept as concept Y

      - concept X is the child of concept Y

      - the title (aka label) of concept X is the string "Y"

      It is the second category that is causing us problems. It includes
      statements such as:

      - this statement was created by A

      - this statement was created on date/time B

      - this statement was made with confidence level C

      - the relevance level of this statement to the news item is D

      - this statement is based on information derived by method E

      We've studied the RDF Primer [3], especially section 4.3 RDF
      Reification [4] and the description given there highlights a number
      of problems. For example, there does not appear to be any way,
      within an RDF graph, to identify a specific instance of a triple.
      So it seems that we couldn't express:

      - Fred said on 22 Dec 2005, with a confidence of 40%, that
      a subject of this news item is concept X.

      The section seems to offer two semi-viable options:

      - Use rdf:ID to identify a statement and then make statements about
      the identified statement.

      - Use some other, application-specific, way to identify statements
      but then don't expect anyone else to understand it.

      We're not clear how either of these would be represented in the
      various triples notations and we're not sure which path to follow.

      Any advice would be gratefully received, especially if reading it
      does not require the consumption of large quantities of headache
      remedy.

      [1] http://www.iptc.org/dev/
      [2] http://www.w3.org/2001/sw/BestPractices/HTML/2006-01-15-rdfa-primer
      [3] http://www.w3.org/TR/2004/REC-rdf-primer-20040210/
      [4] http://www.w3.org/TR/2004/REC-rdf-primer-20040210/#reification

      Misha Wolf
      News Standards Manager, Reuters, www.reuters.com
      Chair, News Metadata Framework WG, IPTC, www.iptc.org/dev
      Vice-Chair, NewsML 2 Architecture WP, IPTC, www.iptc.org/dev


      To find out more about Reuters visit www.about.reuters.com

      Any views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of Reuters Ltd.
    • Misha Wolf
      Thanks for all help with this complicated matter. A new version of the XSLT stylesheet is now available in:
      Message 2 of 2 , Dec 23, 2005
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        Thanks for all help with this complicated matter.

        A new version of the XSLT stylesheet is now available in:
        http://groups.yahoo.com/group/newsml-2/files/Contributed-Tools
        and is called:
        NewsML2-N3_3.xsl

        This version generates N3 output (as opposed to NT) and handles most
        statements about statements, using the RDF reification vocabulary.
        We continue to be unsure whether this is the best approach. If the
        graphing facility in the W3C RDF Validator was working, we could
        convert the triples to RDF/XML and feed the result to the Validator,
        to see the graphs it generates. The graph given in the RDF primer
        for the example using the reification vocabulary isn't exactly
        intuitive.

        Any further advice would be most welcome. Others must have grappled
        with this problem. Is there a preferred solution?

        Misha Wolf
        News Standards Manager, Reuters, www.reuters.com
        Chair, News Metadata Framework WG, IPTC, www.iptc.org/dev
        Vice-Chair, NewsML 2 Architecture WP, IPTC, www.iptc.org/dev


        To find out more about Reuters visit www.about.reuters.com

        Any views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of Reuters Ltd.
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