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Re: Statements about statements -- Help needed!

From: Russell Duhon <fugu13@mac.com>
Date: Thu, 22 Dec 2005 13:54:48 -0500
Message-Id: <28DB63BD-85E0-42DC-9A5F-76C4EA968A59@mac.com>
Cc: Semantic Web <semantic-web@w3.org>, newsml-2@yahoogroups.com
To: Misha Wolf <Misha.Wolf@reuters.com>

The reification approach would likely be a good bet.

I've worked up a quick example, working from content in your model  
draft ( http://www.iptc.org/NAR/1.0/specification/DRAFT-NAR_1.0-spec- 
Model_12.pdf ) and an example in the RDF Primer.

Here's how it might look (fragmentary, of course):

random:triple1	rdf:type				rdf:Statement .
random:triple1	rdf:subject			random:item42 .
random:triple1	rdf:predicate			newsml:provider .
random:triple1	rdf:object			"iptc.org"^^xsd:string .
random:triple1	newsml:confidence 	"0.4"^^xsd:float .

You could create subtypes of Statement that took various properties  
(such as newsml:confidence) if some statements had one set of  
properties and some statements another.

I haven't worked too much with reification in RDF, but this seems a  
fairly straightforward application of the notion, and its a fairly  
elegant way to handle this sort of thing. I could see some  
interesting applications that filtered your RDF based on properties  
of Statements . . . actually, that's a really neat idea. I'm going to  
have to think about how that might be applied to give organizations  
fine-grained control over the statements they make available through  
(perhaps) SPARQL endpoints.


On Dec 22, 2005, at 12:27 PM, Misha Wolf wrote:

> 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.
Received on Thursday, 22 December 2005 18:55:03 UTC

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