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Re: [Fwd: Re: [DTB] Datatypes and Built-ins first run to clean up and extend the initial list]

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Tue, 04 Mar 2008 09:00:55 +0000
Message-ID: <47CD0FC7.8030502@hplb.hpl.hp.com>
To: Jos de Bruijn <debruijn@inf.unibz.it>
CC: axel@polleres.net, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

Jos de Bruijn wrote:

>> Of course, that alternative version wouldn't have any problem, sure.
>> But what I wanted to say is that *nobody* does it like that.
>> Everybody uses option 1 below and not option 2.
>> Option 1:
>>>> <http://www.polleres.net/foaf.rdf#me>
>>>>     foaf:phone <tel:+35391495723> ;
>>>>     foaf:homepage <http://www.polleres.net/> .
> I am wondering why you would want to extract telephone numbers or even 
> IRIs from identifiers in a rules language. The agent that is actually 
> going to make the phone call or browse the homepage will use the 
> syntactical representation of some query answers.

Axel's point was that there are different vocabularies which use 
different encodings (Foaf and vcard in Axel's example). One of our core 
agreed use cases for RIF is translation between vocabularies in 
precisely this way. This has nothing directly to do with the end agents 
it is part of mediating between those agents.

RIF's apparent inability to meet this use case is of serious concern for 
me but unfortunately I don't have a proposed solution.

>> But I am unsure whether we can by any means accomodate for that.
>> Anyway, I think that casts are not trivial to define even for typed
>> literals or no? Since the lex-to-val mapping is not injective in 
>> general, how can I define for instance  the cast
>>    xsd:string( "01"^^xsd:integer)
> we should use the definition of XQuery functions; i.e., use the 
> canonical representation of integers.

I can see some sense in that. However, in practice users place 
unreasonable demands on round tripping. In Jena we preserve both the 
lexical form and the value form of typed literals and distinguish 
semantic equality from Java equality as the only way to satisfy user 

I would prefer the RIF definitions to be compatible with SPARQL and not 
imply any normalization of lexical form of supplied values, of course 
computed values must use a canonical lexical form.

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Received on Tuesday, 4 March 2008 09:01:23 UTC

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