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Re: ISSUE-61 (IRI-Casts): Casting to/from rif:iri [DTB]

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Tue, 10 Jun 2008 16:40:04 +0200
Message-ID: <484E9244.1000907@inf.unibz.it>
To: Rule Interchange Format Working Group WG <public-rif-wg@w3.org>

See [1] and preceding the messages in the thread for a description of 
the semantic problems.  In [1] I also proposed a casting predicate that 
seems to work.

In summary, the biggest semantic challenge in casting IRIs to strings is 
that several different IRIs may be mapped to the same string.  The 
following was my proposal:

"Let I be an interpretation, let u be an element in the domain of I, and
let {i1, ..., in} be the set of IRIs that denote u, i.e. for each ij (1
<= j <= n), IC(ij)=u.  IR(iriToString)(u,"ij")=t for (1 <= j <= n);
IR(iriToString)(u,s)=f for every element s not in {"i1", ..., "in"}."

The rule set
iriToString("b"^^rif:iri,"b"^^xsd:string)

is satisfied in every RIF interpretation.

I think this predicates should be sufficient for most of the use cases.


Best, Jos

Rule Interchange Format Working Group Issue Tracker wrote:
> 
> ISSUE-61 (IRI-Casts): Casting to/from rif:iri [DTB]
> 
> http://www.w3.org/2005/rules/wg/track/issues/
> 
> Raised by: Christopher Welty
> On product: DTB
> 
> It is clear users of RIF dialects such as BLD will want to be able to convert (cast) instances of rif:iri to/from other datatypes, in particular strings and possibly rif:text.
> 
> In general, a casting mechanism is not present in DTB and should be added.
> 
> 
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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Received on Tuesday, 10 June 2008 14:39:25 GMT

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