W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2002

Re: missing (and incorrect) RDFS axioms

From: pat hayes <phayes@ai.uwf.edu>
Date: Sat, 9 Nov 2002 14:59:06 -0600
Message-Id: <p05111b43b9f326696547@[65.217.30.130]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org

>At 09:34 PM 11/8/02 +0100, Jos De_Roo wrote:
>>  > > > rdf:object          rdfs:range  rdfs:Resource .                   *
>>>  >
>>>  > ...did we agree that all literals are resources?
>
>Er... what *is* a literal here:   if, for some datatype, we have:
>
>     v = L2V(l)
>
>is l the literal, or v?   I think v is a resource (member of IR) but 
>l is not necessarily so.

Agreed, except that since l can be used in an untyped literal, it has 
to be a resource in any case. All unicode strings, and pairs of them, 
are resources.

>
>I think Jeremy's argument applied to v.
>
>Intuitively, I would say that l is the literal, not v.  E.g. the MT 
>draft, section 1.2, describes a literal as a "referring expression".
>
>But in another message, Pat says:
>>aaa ppp <any literal, even a bad one>
>>
>>-->
>>
>>aaa ppp _:xxx .
>>_:xxx rdf:type rdfs:Literal .
>
>which seems to be saying that v is the literal (if a literal is any 
>member of rdfs:Literal).

No, no, no. The things in the class rdfs:Literal are the literal 
VALUES. There is no way to talk *about* RDF literals in RDF, just as 
there is no way to talk about urirefs (well, except, in each case, by 
using appropriate datatypes.)

>This is borne out by the MT draft (e.g. section 3.3.1).
>
>I'm beginning to wonder what is the point of rdfs:Literal.

It would be better called rdfs:LiteralValue, but I expect its too 
late to change that now.

>  Fort example, looking at:
>    rdfs:comment rdfs:range rdfs:Literal
>that simply seems to say that the range is a value that *can* be 
>expressed using a literal, not that it *must* be expressed that way. 
>Which I think is quite right.

Me too, particularly as there isn't anything that can ONLY be 
expressed as a literal, given the possibility of defining a URN to 
mean anything the owner wants it mean.

Pat


>Why do we care?
>
>#g
>--
>
>At 09:34 PM 11/8/02 +0100, Jos De_Roo wrote:
>>  > > > rdf:object          rdfs:range  rdfs:Resource .                   *
>>>  >
>>>  > ...did we agree that all literals are resources?
>>
>>well, it's in the current MT draft
>>rdfs:Literal rdfs:subClassOf rdf:Resource .
>>(and I, for one, strongly agree)
>>
>>>  regardless, it's redundant to say range Resource.
>>>  Please let's don't.
>>
>>I agree and try to avoid it in
>>http://www.agfa.com/w3c/euler/rdfs-rules
>>(which is still in a web with owl)
>
>-------------------
>Graham Klyne
><GK@NineByNine.org>


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Received on Saturday, 9 November 2002 15:58:43 EST

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