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Re: datatypes and MT (#rdfms-graph)

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Tue, 13 Nov 2001 20:05:39 -0600
Message-Id: <p05101045b8177eb6138f@[65.212.118.147]>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org
>Brian McBride wrote:
>>
>>  Pat Hayes wrote:
>>
>>  [...]
>>
>>  >
>>  > I thought we had a kind of working consensus to use the graph as the
>>  > 'primary' syntax.
>>
>>  We have more than that.  We have a decision made at the F2F
>>
>  >    http://www.w3.org/2001/sw/RDFCore/20010801-f2f/#decisions
>
>There are several decisions there. Which one are you referring to?
>This one?
>
>"The model theory will be defined for RDF graphs, not n-triples."
>
>Are you suggesting that issues #rdfms-graph is actually closed,
>then? I don't think it's clear what an "RDF graph" is at all.

Well, I guess I did think that was pretty much decided, yes, modulo 
some issues about various kinds of 'tidiness'. Of course we can 
always change our minds, eg I'd be very happy to have literals as 
subjects; but I see that as a change, not settling a currently open 
issue.

>I think that's what we're discussing. I'm suggesting this
>as a definition of an RDF graph:
>
>         terms:
>                 constants (URIs w/fragids)
>                 string literals
>                 bnodes (existentially quantified variables)
>         statement:
>                 term term term.
>         formula:
>                 statement*

But that clearly isn't a definition of a *graph*, right? Its  an 
N-triples -style lexical syntax for specifying graphs, at best, so we 
still need to settle all the tidiness questions. So what this amounts 
to is: to allow literals in subject position (OK with me) and as arc 
labels (OK I guess, but seems kind of silly, eg how would we do 
datatyping of those?) and also have nodeId-style labels on arcs, to 
quantify over properties.

Now, that last idea seems to me to basically break the graph syntax 
proposal; there really isn't any point in having a graph syntax if we 
have to include a labelling device to provide a lexical way of 
indicating identity, rather than relying on the graph structure 
itself. We might as well just give up on the F2F decision you cite 
above, and use Ntriples (suitably relaxed, as you suggest) as the 
primary syntax.  Don't get me wrong; I can live with that; I have no 
trouble with bound variables, and the MT can handle existential 
properties. But there is considerable social evidence that many 
people have a lot of trouble with it; and more to the point, I really 
think that it amounts to a reversal of the decision about making the 
graph primary. It certainly is a rejection, in effect, of the 
*reasons* why that decision was made, viz. to get rid of bound 
variables (local names, anonymous things that had names anyway, 
skolems, whatever you want to call them) from the primary syntax. .

Pat


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Received on Tuesday, 13 November 2001 21:05:38 EST

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