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Re: new semantics initiative

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 13 Jun 2002 10:59:54 +0300
To: "ext R.V.Guha" <guha@guha.com>
CC: Pat Hayes <phayes@ai.uwf.edu>, Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>, Jonathan Borden <jonathan@openhealth.org>
Message-ID: <B92E2BAA.16A84%patrick.stickler@nokia.com>


On 2002-06-12 18:27, "ext R.V.Guha" <guha@guha.com> wrote:

> Patrick,
> 
>  The darkening (or more appropriately, non-lightening) mechanism has to be in
> the step that goes from the syntax (i.e., the graph) to assertions (i.e.,
> statements in Lbase or in the definition of satisfaction). This "flag" has to
> be based on some aspect of syntax, i.e., it cannot depend on entailment.

Do you mean that the distinction must be based on URI inspection? (I hope
not).

My proposal was that there would be a distinction in the graph syntax. In
NTriples, unasserted statements are either prefixed with a special character
or terminated differently from asserted statements.

As to what you wish to use in the MT notation, feel free to do as you
think best.

I don't see how anything I proposed depends on entailment. Can you clarify?

> The 
> namespace hack is one possibility.

No it *isn't*. Namespaces do not exist in the graph and URIs are opaque.

If you are talking now about graph syntax, then namespaces simply
do not exist.

> That might be other possibilities.

I've already proposed some. Perhaps you can clarify why they are not
suitable.

Cheers,

Patrick

> guha
> 
> Patrick Stickler wrote:
>> On 2002-06-12 7:23, "ext patrick hayes" <phayes@ai.uwf.edu>
>> <mailto:phayes@ai.uwf.edu>  wrote:
>> 
>>   
>>> ...instead, we (ie the RDF coreWG) assume that the W3C will
>>> eventually have the good sense to declare that a certain namespace is
>>> *globally* understood to be 'rdf-invisible', in that any triples
>>> which use urirefs from that namespace are not asserted in any RDF
>>> graph.
>>>     
>> 
>> Sorry to rain on the parade, but this is nonsense. Namespaces
>> are not significant nor represented in the RDF graph, and there
>> is no formal relationship between a URI and whatever namespace
>> prefix was used to hack it into the RDF/XML serialization.
>> 
>> Basing the designation of dark triples on namespace distinction
>> is impossible, since that distinction is an illusion.
>> 
>> C.f. http://lists.w3.org/Archives/Public/www-rdf-interest/2002Jun/0172.html
>> 
>> If you wish to simply say that the use of namespaces to trigger
>> an RDF parser to flag such statements as dark, well, fine, but
>> let's please be clear that it is a syntactic mechanism and not
>> a semantic one, and to that end, I can think of a number of
>> other possible (and IMO better) syntactic mechanisms for
>> indicating dark triples that are not based on namespace prefixes.
>> 
>> But saying "any triples which use urirefs from that namespace"
>> is nonsense since urirefs have no namespace. They are URIs,
>> not qnames, and they are fully opaque.
>> 
>> Presuming that triples have some indication of being dark
>> which is not based on namespaces, such as a simple bit,
>> then we're OK, and can proceed with dark triples and
>> the introduction of the proposed layering tweaks to the MT.
>> 
>> But there are *no* namespaces in the RDF graph. None whatsoever.
>> 
>>   
>>> (6) Does this require any changes to syntax/ test cases/ Ntriples/
>>> datatyping/ whatever?
>>> A: No.
>>>     
>> 
>> I don't see how it would not. We would need a mechanism in RDF/XML
>> for setting the dark bit on statements and also an explicit
>> representation of that bit in NTriples (such as ';' rather than '.').
>> 
>> But that probably is not a great amount of work, and likely
>> could be done in a backward compatable manner.
>> 
>> [In case it's not clear, I'm pretty much in favor of providing for
>>  these layering tweaks to the MT and elsewhere, so long as they
>>  are not based on reference to namespaces]
>> 
>> Cheers,
>> 
>> Patrick 
>> 
>> --
>>                
>> Patrick Stickler              Phone: +358 50 483 9453
>> Senior Research Scientist     Fax:   +358 7180 35409
>> Nokia Research Center         Email: patrick.stickler@nokia.com
>> 
>>   
> 

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Thursday, 13 June 2002 03:55:48 EDT

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