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Re: rdfs:Statement for Qualified Predictates

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 04 Aug 2004 23:36:39 +0100
Message-Id: <>
To: Matthew Leingang <leingang@math.harvard.edu>, <www-rdf-interest@w3.org>

A recent draft [2] put out by the Semantic Web Best Practices and 
Deployment Working Group [1] might have some useful ideas for you:


[1] http://www.w3.org/2001/sw/BestPractices/

[2] http://www.w3.org/TR/swbp-n-aryRelations/

At 16:42 04/08/04 -0400, Matthew Leingang wrote:

>Hi all,
>Long time lurker, first time poster.
>I'm thinking about generating RDF from my Books [1] database to publish
>online (why not? :-). Books allows you store lots of data, not only about
>the book, but when you got it, who you loaned it to, etc.
>How does one best put something like "I have owned this book since August 1,
>2004" in RDF?  Without the date I could just say
>:me foaf:owns [a book:Book; book:isbn "012345678"] .
>(assuming we have a book schema someplace with a Book class and isbn
>property).  With the date we have a qualification of the foaf:owns property.
>When implementing this first in python, I started creating
>"AgentObjectAssociation" classes for want of a better term.  Then about a
>day later I realized that these AgentObjectAssociations were just subclasses
>of regular RDF triples.  It seems, then, that you can do this by reifying
>the statement and adding whatever other properties & types you want:
>[a rdfs:Statement;
>    rdfs:subject :me;
>    rdfs:predicate foaf:owns;
>    rdfs:object [a book:Book; book:isbn "012345678"];
>    a ical:Vevent;
>    ical:dtstart "2004-08-01".]
>I don't know if this is a misuse of ical to talk about *any* event, not just
>one that one might schedule in a PIM tool.  But another schema for events
>could be used if necessary.
>I recall from the one of the RDF TR's that the set of statements
>[a rdfs:Statement; rdfs:subject :a; rdfs:predicate :b; rdfs:object :c]
>doesn't necessarily have to imply :a :b :c (which is a good thing:
>"declaring 'Mission Accomplished' doesn't make it so"!) and that made me shy
>away from using qualified statements like this.  But it seems useful.
>Another use would be to give the authority of a statement, so an agent can
>decide which one to accept:
>[a rdfs:Statement;
>    rdfs:subject    :LeeHarveyOswald;
>    rdfs:predicate  :killed;
>    rdfs:object     :JohnFKennedy;
>    dc:creator      :WarrenCommission
>[a rdfs:Statement;
>    rdfs:subject    :Mafia
>    rdfs:predicate  :killed;
>    rdfs:object     :JohnFKennedy;
>    dc:creator      :OliverStone
>Sorry if my N3 is off, but hopefully you get my drift.  So I guess I'm
>asking is: is this "in or out of line" (to borrow the question of a previous
>poster)?  Are there other ways to employ adverbial prepositional phrases
>like "since" or "according to" in RDF?
>Thanks for any help.
>--Matthew Leingang
>[1] http://books.aetherial.net/
>Matthew Leingang
>Preceptor in Mathematics
>Harvard University
>URL: http://www.math.harvard.edu/~leingang/
>vCard: http://www.math.harvard.edu/~leingang/vCard.vcf

Graham Klyne
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Received on Wednesday, 4 August 2004 18:48:21 UTC

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