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Re: Dave Reynolds: rdf:text - clarification requested

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Wed, 10 Dec 2008 12:03:06 +0000
Message-ID: <493FAFFA.7080603@hplb.hpl.hp.com>
To: Axel Polleres <axel.polleres@deri.org>
CC: Sandro Hawke <sandro@w3.org>, public-rdf-text@w3.org, "Seaborne, Andy" <andy.seaborne@hp.com>

Axel Polleres wrote:
> Sandro Hawke wrote:
>> [moving Dave's e-mail to the joint list]
>>
>> (fwiw, I agree with Dave's comment/concern, as I suspect do we all.)
>>
>>      -- Sandro
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> Subject:
>> rdf:text - clarification requested
>> From:
>> Dave Reynolds <der@hplb.hpl.hp.com>
>> Date:
>> Tue, 09 Dec 2008 15:58:40 +0000
>> To:
>> RIF WG <public-rif-wg@w3.org>
>>
>> To:
>> RIF WG <public-rif-wg@w3.org>
>>
>>
>>
>> Please could I get some clarification on the following line from the 
>> rdf:text document:
>>
>> """In addition to the RIF and OWL specifications, this datatype is 
>> expected to supersede RDF's plain literals with language tags, cf. 
>> [5], which is why this datatype has been added into the rdf: 
>> namespace. """
>>
>> I don't recall any discussion on this notion of "supersede". What 
>> exactly is being proposed here? I have been regarding rdf:text as a 
>> formalization of RDF plain literals with language tags which 
>> simplifies OWL2/RIF's job but is not a change to RDF.  Clearly any 
>> change to the RDF specs would have implications for tools developers, 
>> especially if there are any round-tripping requirements, and wouldn't 
>> be something to make likely. I don't think it appropriate to hint at 
>> such a change in the rdf:text document without more details.
>>
>> Apologies for not having noticed this line earlier.
>>
>> Dave
> 
> My personal opinion: I is not the intention to change/affect the 
> existinfg RDF specs, but the datatype is indeed intended to fix the 
> mismatch between plain literals and language tagged literals for 
> impementations which adopt it.

Is that something that needs "fixing"?

In i18n terms then internationalized text and strings are quite 
different things. The differences between the two in RDF have not been a 
problem in implementations or practice that I'm aware of. Is there any 
evidence to suggest otherwise?

I thought rif:text, now rdf:text, was invented to simplify including 
internationalized strings in RIF not to fix some problem with RDF.

> Any suggestion for a rewording that would rather convey this message?

We need clarity on what is being proposed before thinking of a wording.

Are you intending or expecting that RDF implementations should 
explicitly support rdf:text as a datatype?

So that they would regard:

(a)    eg:a eg:p  "foo"@en .

and

(b)    eg:a eg:p  "foo@en"^^rdf:text .

as equivalent graphs?

Would there be any expectation on round tripping so that an RDF 
processor receiving a graph in form (b) would be expected to return it 
in the same form and not normalize it to form (a)?

When we originally proposed rif:text I was expecting to translate RDF 
lang-tagged literals to rif:text as part of a translator and rif:text 
would not appear as a datatype in the RDF.

Implementing rif:text as a RDF datatype is clearly possible but the 
discontinuity introduced by changing RDF would be a serious concern. We 
could end up in a state where some RDF producers thought form (b) was a 
legal way to exchange an internationalized text fragment in RDF while a 
fraction of deployed RDF consumers would not consume it (at least not 
with the required semantics).

If only RIF and RDF were involved then my preferred phrasing would be 
something like:

"Note that the rdf:text datatype is purely intended for use within RIF 
and it is not intended that RDF processors should support this as an RDF 
datatype. Consumers of RDF-RIF combinations are expected to map between 
RDF language-tagged literals and rdf:text literals as part of the RIF 
translation process."

Indeed it might be better still to substitute "SHOULD NOT" (in the 
RFC2119 sense) for "not intended".

However, that doesn't cover OWL2. I don't understand enough of OWL2's 
requirements here, and how interoperation with deployed RDF is 
envisaged, to be able to suggest anything specific.

Dave
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Received on Wednesday, 10 December 2008 12:04:00 UTC

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