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Re: RDF's curious literals

From: Sandro Hawke <sandro@w3.org>
Date: Thu, 02 Aug 2007 13:32:24 -0400
To: Story Henry <henry.story@bblfish.net>
Cc: "Sandro Hawke" <sandro@w3.org>, Lee Feigenbaum <lee@thefigtrees.net>, Richard Cyganiak <richard@cyganiak.de>, Garret Wilson <garret@globalmentor.com>, Tim Berners-Lee <timbl@w3.org>, Semantic Web <semantic-web@w3.org>
Message-ID: <15219.1186075944@ubuhebe>


Story Henry <henry.story@bblfish.net> writes:

> > Therefore, X is a datatype if and only if X is an  
> > owl:FunctionalProperty
> > and the rdfs:domain of X contains only Unicode strings.
> 
> well I was proposing in addition that it be a necessary truth, ie it  
> necessarily identify the thing that way,  which will bring up some  
> fun problems, but I think that the intuition behind datatypes is  
> something along those lines.
...
> >> This can only work
> >> of course if all the information is contained in the String, ie,
> >> there is not more information to be got from anywhere else, or else
> >> there would be no way to create a decision procedure for it. So
> >> "George Bush"^^xxx:presidents would not work. For one, George Bush
> >> may never have been president.
> >
> > But it's easy for me to construct the mapping you quoted above.  So I
> > can't understand what you mean.  A datatype like eg:uspresidents makes
> > every bit as much sense as a datatype like xs:date.
> 
> That would not work with eg:uspresidents, because Bush could have had  
> a different name, and  could also not have been president.
> 
> With numbers on the other hand it is different. Even though 10 could  
> be written differently than "10"
> 
> 10 xsd:int "10".
> 
> is necessarily true.

So you're saying the distinction is that datatype lexical representation
strings are rigid designators [1] ?  Hmmm.  Let me think this
through....  

Again, I'll return to my example of dates, rather than integers, since
their being socially constructed is more obvious.  There was an instant
where I paused, in writing this sentence, to record the time.  That
instant is named in RDF as "2007-08-02T17:14:39"^^xs:dateTime.  Is that
a rigid designator?  In a world where the Gregorian calendar corrections
were never adopted, that instant would be named something more like
``"2007-08-16T17:14:39"^^xs:dateTime''.  (etc, etc, with all the
different ways we could do calendars and clocks.)

I think I would argue that URIs are rigid designators, so the example
above fails because I used "xs:dateTime" to name a different mapping.
In the first case it's the Gregorian calendar dateTime; in the second
it's some pseudo-Julian calendar dateTime.  But the string itself,
"2007-08-16T17:14:39" is meaningless/useless without being paired like
that.    It's not the rigid designator itself.

Similarly, my term eg:uspresidents rigidly designates the pairs of names
and presidents in my world.   So, yes, "George W. Bush"^^eg:uspresidents
is a rigid designator -- it necessarily refers to the current president
of the US in my world.

Isn't that right?

   -- Sandro

[1] http://en.wikipedia.org/wiki/Rigid_designator
Received on Thursday, 2 August 2007 17:34:13 GMT

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