W3C home > Mailing lists > Public > semantic-web@w3.org > July 2010

Re: Subjects as Literals

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 1 Jul 2010 14:00:20 -0500
Cc: Ross Singer <rossfsinger@gmail.com>, Hugh Glaser <hg@ecs.soton.ac.uk>, Linked Data community <public-lod@w3.org>, Semantic Web <semantic-web@w3.org>
Message-Id: <B2540380-46EC-4B21-83CF-B17AA4615BEE@ihmc.us>
To: Robert Sanderson <azaroth42@gmail.com>

On Jul 1, 2010, at 10:12 AM, Robert Sanderson wrote:

>
>
> On Wed, Jun 30, 2010 at 9:14 PM, Pat Hayes <phayes@ihmc.us> wrote:
>
> 3. Dates represented as character strings in some known date format  
> other than XSD can be asserted to be the same as a 'real' date by  
> writing things like
>
> "01-02-1481" sameDateAs "01022010"^^xsd:date .
> "01-02-1481" isDateIn :MuslimCalendar .
>
>
> This is a great example of what is wrong with the proposal! :)
>
> Either, the literals stand by themselves and each occurrence of  
> "01-02-1481" is a completely separate instance (and in the current  
> syntax would get a unique identifier), or *all* occurrences of the  
> literal can be conflated together.  The distinction between a token  
> and a type, respectively.

The current RDF model clearly mandates that we understand these as  
types rather than tokens, just like URIs . So I will only respond to  
that alternative.

>
> Option 2: Literal as Type
> However, if all occurrences of that string are the same entity and  
> can be merged together, then we also have:
>
> "01-02-1481" sameDateAs "1481-02-01"^^xsd:date .    // ddmmyyyy
> "01-02-1481" sameDateAs "1481-01-02"^^xsd:date .    // mmddyyyy
> "01-02-1481" isDateIn :RomanCalendar
>
> This also makes the proposal pointless as you cannot say anything  
> meaningful which is globally true about a literal.  That same string  
> is at least three different dates in two different calendars. Drat  
> that pesky global truth requirement!

So, what is the problem? That one string is, indeed, three different  
dates in three different calendars. The string "chat" is one word in  
French, a different word in English. But it is the same string in both  
cases; and the literal denotes the string.

>
> The only way that Pat's example makes sense is if the context of the  
> literal is constrained to the current named graph.  If there was  
> interest in "fixing" RDF, then making Named Graphs a core feature  
> would be my first agenda item!

Well, I agree about the conclusion, but not for this reason.

Pat

>
> Rob Sanderson
>

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Received on Thursday, 1 July 2010 19:01:29 UTC

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