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Re: [ontolog-forum] [Fwd: Re: {Disarmed} Re: OWL and lack of identifiers

To: Pat Hayes <phayes@xxxxxxx>
Cc: Ontolog Forum <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Waclaw Kusnierczyk <Waclaw.Marcin.Kusnierczyk@xxxxxxxxxxx>
Date: Mon, 16 Apr 2007 17:26:09 +0200
Message-id: <46239591.8070803@xxxxxxxxxxx>

Pat Hayes wrote:
>> Pat Hayes wrote:
>>>>  Re: Peter F Brown's post (Sat, 14 Apr 2007 09:35:14)
>>>>  Peter writes:
>>>>  "
>>>>  The spec is clear, yesS. but an object is not the same thing as the
>>>>  address of the object - (according to the RFC, I *am* my address): the
>>>>  object needs identity as much as the address of it does. That is 
>>>> where I
>>>>  feel this axiom of the W3C falls downS
>>>>  "
>>>>  Clearly there is a problem here.  But we should be careful to
>>>>  distinguish confusedly designed frameworks from confused documentation
>>>>  of well-designed ones.
>>>>  While RDF specifications, for example, are relatively clear and sound,
>>>>  the RDF primer provides an abundance of examples such as:
>>>>  ex:index.html  exterms:creation-date  "August 16, 1999" .
>>>>  ex:index.html  dc:language            "en" .
>>>>  supposed to state that "August 16, 1999" is the creation date of a 
>>>> page
>>>>  and "en" is he language of a page, while both are literal strings and
>>>>  *not* identifiers for a date and a language, respectively.
>>>  What??  Why should a string not be an identifier? In fact, it seems to
>>>  me that *all* identifiers are strings. And the second example uses a
>>>  language tag which is taken from an Internet standard for language
>>>  tagging: what could be a better example of an agreed identifier? Why is
>>>  this confused?
>> Hold on.  It is not whether something is a string or not which counts,
>> but how it is to be interpreted.  Of course, "August 16" can be an
>> identifier for anything you may wish.  But it is a string, not a date.
> Of course it is not a date, but it is (using widely accepted 
> conventions) an *identifier* of a date.
>> But as the object of a triple, "August 16" is a literal, not a URI, and
>> in RDF, a literal is (supposed to be) self-referential.
> True. But it is an easy extension to the RDF interpretation to go on to 
> interpret that string as denoting a date. RDF was always intended to be 
> used as part of larger systems of conventions and interpretations.    (01)

Agreed.  But then the discussion of whether a URI means itself or 
something else is also left to other applications, and any complaint 
should be sent there.    (02)

> And this is, after all, an example from a primer. The best way to 
> express this in RDF would be to use a typed literal with the xsd:date 
> system, which is required to exactly denote a date; but the primer had 
> not covered datatyping at this point.    (03)

It did, of course.  (The 2004 version does speak of xml-schema datatypes.)    (04)

vQ    (05)

> Pat    (06)

Wacek Kusnierczyk    (07)

Department of Information and Computer Science (IDI)
Norwegian University of Science and Technology (NTNU)
Sem Saelandsv. 7-9
7027 Trondheim
Norway    (08)

tel.   0047 73591875
fax    0047 73594466
------------------------------------------------------    (09)

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