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

Re: Should rdf:value have a semantics??

From: Frank Manola <fmanola@mitre.org>
Date: Wed, 04 Dec 2002 18:01:36 -0500
Message-ID: <3DEE8950.4090300@mitre.org>
To: Graham Klyne <GK@ninebynine.org>
CC: pat hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org

Graham Klyne wrote:

> At 04:47 PM 12/3/02 -0600, pat hayes wrote:
> 
>>> Back up a minute.  The "historic" use of rdf:value was for the cases
>>> like
>>>
>>> my:cat rdf:type ex:DomesticCat .
>>> my:cat ex:weight _:x .
>>> _:x rdf:value "15" .
>>> _:x ex:unit ex:Kilogram
>>>
>>> Now that we have datatypes, the extension of this usage to
>>>
>>> my:cat rdf:type ex:DomesticCat .
>>> my:cat ex:weight _:x .
>>> _:x rdf:value "15"^^xsd:integer .
>>> _:x ex:unit ex:Kilogram
>>>
>>> seems perfectly straightforward.  You're being more precise about what
>>> the value is (it's a number, rather than a string), and you need other
>>> properties anyway to specify the units (and anything else).  I'm not
>>> such a fan of rdf:value, but it seems to me that restricting rdf:value
>>> to preclude this usage might seem somewhat artificial to those already
>>> using it.
>>
>>
>> Yes, OK, fair enough. Sigh. Then I really don't know what can be said 
>> about it in the MT. So maybe I wont say anything.
>>
>> Neeeverrr Mind.
> 
> 
> OK, even if we can't define it formally, shouldn't we at least try to 
> say something normative about its *intended* meaning -- otherwise 
> discussions like the above will continue to dog any use of rdf:value, 
> and we might be better off deprecating it now.
> 
> The trouble I have is that I don't know what "principle value" means.
> 
>   Q: How long is the wire?
> 
>   A: 10 miles
> 
> I might argue that "miles" is in some sense more "principal" than the 
> associated number 10;  e.g. as opposed to metres.
> 
> Another question, would it be wrong to write:
>   ex:pieceOfWire rdf:value "10" .
>   ex:pieceOfWire rdf:value "miles" .
> ?


I agree that determination of "principal" is in the mind of the 
beholder.  The obvious examples are, well, obvious.  In the case of a 
more complicated structured value (or a simple value where the semantics 
are less common), it might be difficult to figure out which should be 
considered the "principal" value (the Primer sort of suggests that). 
However, keep in mind that saying something normative about the intended 
meanings of such constructs may require a bunch of additional writing. 
For example, we'd need to describe the intended meaning of Alt a lot 
more clearly than it's currently described in any normative document I'm 
aware of.

--Frank



-- 
Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Wednesday, 4 December 2002 17:44:20 EST

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:54:48 EDT