On Jul 1, 2010, at 10:12 AM, Robert Sanderson wrote:
On Wed, Jun 30, 2010 at 9:14 PM, Pat Hayes <[email protected]> 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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