Re: datatypes and RDF Schema

From: Pat Hayes (phayes@ai.uwf.edu)
Date: 10/08/01


>From: Pat Hayes <phayes@ai.uwf.edu>
>Subject: Re: datatypes and RDF Schema
>Date: Mon, 8 Oct 2001 11:06:16 -0500
>
>[... ...]
>
>>  >>  >3/ Use special URIs to refer to these value spaces and 
>>incorporate their
>>  >  > >    meaning into the meaning of RDF Schema.
>>  >>
>>  >>  How does this differ from the proposal that Patrick Stickler has been
>>  >>  outlining on rdf-logic?
>>  >
>>  >Patrick wants, I think, int:20 to be the way you get the integer 20.  This
>>  >proposal does not use qualified literals at all.
>>
>>  If I follow Patrick, neither does he. He wants to eliminate literals
>>  altogether and replace them with typed Qnames.
>
>Which I view as exactly the same as typed literals.  :-)

Hah!  As I suspected, you don't *really* believe in literals, do you?

>I don't care too much whether typed literals are lexicalized as
>
>	<age>int:20</age>
>
>or
>
>	<age type=int>20</age>

I agree the lexicalisation isn't important. What is important, 
though, is whether this is seen as something that is checkable 
directly from the syntax, or if it requires some inference machinery 
which is liable to go off on its own and start navigating search 
spaces.

>
>>  >Instead it uses something
>>  >like xsd:integer to get from the vague notion of 20 to the precise notion
>>  >of the integer 20.
>>
>>  Yawn. Frankly, I personally don't have an axe to grind here. What I
>>  do care about is that some fast, simple, piece of machinery can
>>  determine what the 'type' of any literal is supposed to be
>>  sufficiently tightly that I can assign it a unique value in any
>>  interpretation. It has to be fast and simple enough to be thought of
>>  as part of the lexical/parsing machinery, not part of the general
>>  inference process.
>
>The point of discussion is, I think, how much work it is to determine that
>a mention of 20 has ``type'' xsd:integer.  I'm arguing that there can be
>benefits to having a heavy-weight (i.e., semantic), but special-purpose
>mechanism.  I think that you are arguing that to make sense, the
>special-purpose mechanism has to be light-weight (i.e., syntactic).

Right, though I wouldn't say that it HAS to be that way in order to 
make sense. However I do think that having it that way (which may 
only be a matter of nomenclature in the metatheory, in fact, rather 
than any really deep distinction) is both practically important and 
keeps the overall theory cleaner. Also I worry that there is a danger 
of the 'heavy-weight' mechanism (which I confess to not really 
following in detail) simply becoming indistinguishable from the 
general inference machinery, at which point we have simply given up 
on the very idea of literals, in all but name.

BTW, re. your recent rants about communication. This issue is being 
discussed simultaneously both here and on RDF-core, and I'm sure it 
would be extremely useful if the discussions could be integrated. 
Take a look at the rdfcore email archive this month under 'big 
issue', I'd be very interested on your (or anyone else's) comments on 
this stuff, particularly on 
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Oct/0076.html.

Pat

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