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Re: suggested wording for removing weasels from MT

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Wed, 24 Apr 2002 08:45:06 +0100
Message-Id: <5.1.0.14.2.20020424083452.03a0ad00@joy.songbird.com>
To: Dan Connolly <connolly@w3.org>
Cc: Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg@w3.org
At 03:19 PM 4/23/02 -0500, Dan Connolly wrote:
>On Tue, 2002-04-23 at 14:52, Pat Hayes wrote:
> > Well, I have to say something about what it means to 'assert' an RDF
> > graph. The document already makes some vague noises about one graph
> > being taken to include a merge of any other graphs that are thought
> > to define its vocabulary,
>
>It does? Where did that come from?
>
>The nice thing about a model theory is that it *eliminates*
>things like vague noises. I hope we have no vague noises
>anywhere in the model theory spec.

My take on this was that if one chooses to merge the vocabulary definition 
with the statements that use that vocabulary, the model theory gives a 
consistent reading of the resulting graph.  The meaning is well defined, 
but whether one chooses to merge the graphs in this way is less so.

> > so it seemed harmless to add that some
> > users might want a graph to assert *less* than is actually in it. I
> > don't see this as a "hook", since it doesn't even hint at any way to
> > implement or use this,
>
>
>No? I read it (and I think lots of other people would read it)
>as saying "well, you know those entialment tests? sometimes
>they work, but not always. It depends, really, on
>fuzzy stuff that we're waving our hands around but not
>actually specifying."

Again, my take was that dark triples, if present, must be clearly indicated 
in some syntactic way to avoid this kind of vagueness.

> > just an acknowledgement that people do
> > sometimes do things like this (some of them people on the WG itself,
> > in fact)
>
>For example?

I guess this means referring to a separate graph, and saying it's not 
asserted, which I've heard mentioned.  I'm very uncomfortable with that.

I think the model theory is silent about the meaning of multiple graphs 
*until they are merged*.  SO if we are to have dark triples, I think they 
need to be distinguished within a single graph.

> >  The only
> > normative aspect of this is that the MT (now with no clauses in it
> > about unasserted triples) defines the content of whatever is
> > asserted; that is unambiguous and unqualified.
>
>Yes, and the syntax spec tells us the connection between
>a hunk of XML and what's asserted (i.e. a graph of asserted
>triples). I want to make sure that the connection between
>RDF/XML and the various entailments is rock solid, with no
>weasel words in between.

Yes.

>I prefer to resolve conflicts at the earliest possible opportunity.
>If the layer cake goes up in smoke as a result of being clear
>what a hunk of RDF/XML means, then so be it. Let's do that
>quickly so we can get on with something else.

The layer cake is a useful pedagogical device, in that it illustrates some 
future goals, but I have my doubts that the various pieces will turn out to 
be related just as shown there.

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Wednesday, 24 April 2002 03:37:08 EDT

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