Re: Comment on "Meaning and the Semantic Web"

On Jun 1, 2004, at 9:12 PM, John Black wrote:

>> -----Original Message-----
>> From: Dan Brickley [mailto:danbri@w3.org]
>> Sent: Wednesday, May 05, 2004 4:10 AM
>> To: John Black
>> Cc: public-sw-meaning@w3.org
>> Subject: Re: Comment on "Meaning and the Semantic Web"
[snip]
>> For example, I can, it is commonly supposed, change the OWL/RDFS/HTML
>> at http://xmlns.com/foaf/0.1/ and alter the (ahem) meaning of
>> thousands (millions, actually) of RDF/XML documents. By editing a few
>> files and typing 'make site', I can make docs that weren't currently
>> true of the world, true of the world; and vice-versa.
>
> But this is true if you owl:import http://xmlns.com/foaf/0.1/ also,
> isn't it?

So, using owl:imports introduces a dependancy that just using the terms 
doesn't.

You could also cut and paste the FOAF ontology into your document by 
hand. That would, on our view, preserve you from not-in-your-control 
meaning shifts.

You could also import http://foo.com/myfoafmirror/ (pace copyright 
issues) (which actually might come up with owl:imports). The imported 
document could use the foaf prefix and provide more stabilty.

>  So the imports-only proposal offers no defense against this.

Sure it does. See above. It may

> The meaning of documents under this proposal is just as dependent on 
> the
> stability of the ontological context it imports as other documents are
> dependent on the stability of the schemas whose namespaces they 
> include.

Except that imports and URI use are separated. So you have more 
flexibility. We didn't claim it was a *grand* solution, only one with a 
bit of critical flexibility.

>> Since I'm a reasonably responsible person, this is probably not a big
>> deal. I promise to be good. But try explaining that to someone
>> building an ecommerce system that depends upon  externally-managed RDF
>> vocabularies.
>
> Right.  And now that you have explained it, I will refrain from using 
> FOAF
> for anything serious until I have a way to make sure my documents are
> interpreted using the exact version of the FOAF spec that existed when
> I wrote them using that namespace or when I imported it.

In my view, you have it now. Cut and paste, or mirror and import. Are 
this horky, sure. But at least they, in fact, work. This is all we were 
advocating.

>  Personally,
> I predict that you *WILL* change it at some point in a way that changes
> the meaning of millions of statements. And this is the point Tim was 
> trying
> to make, I believe, when he said "that use of a URI in RDF implies a
> commitment to its ontology."

What? Your prediction is Tim's point? Sorry, lost me.

> http://lists.w3.org/Archives/Public/www-tag/2003Jul/0022.html For, 
> just as
> changing the FOAF spec. would alter the sense of millions of documents,
> failure to use the correct FOAF spec., when interpreting some RDF 
> document
> dependent upon it, would alter the sense of the document.

Still lost, sorry.

Hmm. I *think* you mean that, sans import, if I fail to (in effect) add 
the imports in, then I've changed the meaning of the document? Piffle. 
Not *my* documents. Refraining from an imports seems to me to be a 
powerful way to signal what I mean by foaf:knows (*not* in the Biblical 
sense).

This is a difficult point for a number of reasons. For example, part of 
the point of moving to a machine processible formalism is so that the 
*formalism* can encode the "specification". But our specs aren't 
separate from the things they "specify" -- that is, it's very much 
unlike the relationship between a grammar and the strings recognized.

Oh wait, I see. Sure, when interpreting *some RDF document dependent 
upon the correct FOAF spec* (for its meaning). But, sans imports, 
there's no way in rdf to indicate that dependancy. And that's fine. RDF 
meaning is perfectly reasonable. If I want to conform to some other, 
tighter spec, there are any number of ways to indicated that.

>   If it is "good"
> of you to refrain from changing the spec. in this way, it seems it 
> would
> be similarly good of you to use the spec., that is commit to it, when
> interpreting someone's URIs.

Hardly. In one case *you* affect the meaning of *my* documents. In the 
other, my different use doesn't affect the meaning of *your* uses. If 
the difference, thus put, isn't brutally obviously, then I'm at a 
complete loss.

>   The scale is different but the effect is
> the same.

Clearly not.

>   By refusing to respect the ontological context of a document,
[snip]

You are imposing this very specific notion of ontological context. It 
happens not to be in any spec, nor is it, contra some view, at all 
imposed by web architecture. You can propose it, but I, for one, will 
vigorously resist.

But I feel like there must be a thinko here. I'm finding this symmetry 
argument impossible to take seriously.

Cheers,
Bijan Parsia.

Received on Tuesday, 1 June 2004 22:02:21 UTC