W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2001

Re: ACTION 2001-08-24#9 : issues with containers

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 4 Sep 2001 12:55:53 -0700
Message-Id: <v04210107b7badf557a0d@[130.107.66.237]>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org
>Jan Grant wrote:
>[...]
> > While I have held, in principle, what I'd characterise as DanC's opinion
> > here (or the more extreme version: "alt is totally broken")
>
>I'm not saying it's broken; I'm just saying it's not magic.
>It's very mundane; from the MT perspective,
>it means no more or less than any
>other class (Apple, Bananna, Integer, ...).

Then why bother even mentioning it in the M&S, let along spending 
pages on it? The M&S doesn't seem to feel a compulsion to go on and 
on about recommended uses of Bananas.

> > - that is,
> > that an app can infer what it likes, an alt-unaware MT is going to
> > produce an odd semantics for something like
> >
> >      <doc1> <dc:creator> _:a .
> >      _:a <rdf:type> <rdf:Alt> .
> >      _:a <rdf:_1> <jan> .
> >      _:a <rdf:_2> <dan> .
> >
> > ("doc1 was written by either jan or dan") - I don't see how you can
> > ignore alt in the MT and get this interpretation, no matter how you go
> > about it.
>
>I interpret that n-triples fragment not as "doc1 was written
>by either jan or dan" but
>
>  doc1's has a creator value which is a collection including
>  jan and dan; this collection is the sort where folks conventionally
>choose
>  one from the collection, rather than using all of them.
>
>Again, suppose the graph had a Bag rather than an Alt:
>
>      <doc1> <dc:creator> _:a .
>      _:a <rdf:type> <rdf:Bag> .
>      _:a <rdf:_1> <jan> .
>      _:a <rdf:_2> <dan> .
>
>We don't license the inference that
>	<doc1> <dc:creator> <jan>.
>in that case, do we? No. Then why should rdf:Alt have any magic
>associated with it?

Because that is what the M&S seems to imply, seemed to me; and 
because if we can't infer anything different from its being an Alt 
than a Bag, why does the language have both constructs in it? It's 
not a question of 'magic', but of understanding why there would be a 
totally meaningless distinction built into the syntax.

This line amounts to treating all containers alike in the MT, ie they 
are thingies that have elements which are accessed by applying rdf:_n 
to them, and that's all. The only differences between bags and seqs 
and alts is that they are different by stipulation, ie nothing can be 
both of them at once.

However, if we do say this, then it seems question-begging (and 
intellectually dishonest) to go on to say that some aspect of meaning 
is 'conventionally' this or that, when the language itself doesn't 
support that 'conventional' interpretation. In other words, we are 
saying that it *does* mean something, nudge nudge wink wink, but *we* 
aren't going to come out and say what it does mean, for some reason. 
(Not that we couldn't: we can, in fact, but we are refusing to, for 
some reason, probably because ... well, I cannot think why, to be 
honest. )

This seems to me to be exactly the wrong way to set up a useful 
semantic-web information interchange language.

Pat

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Received on Tuesday, 4 September 2001 15:54:37 EDT

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