W3C home > Mailing lists > Public > public-sw-meaning@w3.org > March 2004

Re: Self-descriptive assertions

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Fri, 26 Mar 2004 13:05:00 -0500
Message-Id: <192BB27E-7F50-11D8-AEC8-0003939E0B44@isr.umd.edu>
To: public-sw-meaning@w3.org

On Mar 26, 2004, at 12:46 PM, Mark Baker wrote:

> On Fri, Mar 26, 2004 at 11:25:08AM -0500, Bijan Parsia wrote:
>>> Yes, exactly.  That's what I mean by "communicate the graph".  If I
>>> use text/plain, I'm not communicating the graph, because the message
>>> doesn't include any information would inform a recipient that the
>>> message semantics depend on the RDF specs.
>> This is a total non-starter, IMHO. It doesn't work either way: I don't
>> necessarily "communicate the graph" by using application/rdf+xml 
>> (think
>> about a tutorial on the hidiousity of RDF/XML), nor do I necessarily
>> *fail* to "communicate the graph" by not using it.
> I'm quite certain that you do, in both cases.

Well, you are at least wrong about me. And I'd love to see spec text 
that even *suggests* that.

>> Note that by your model, there's no way to "communicate" an owl
>> ontology (since we don't have an owl mimetype).
> But is an OWL ontology any more than an RDF graph?

Yes. Radically different semantics.

>   AFAIK, it isn't.
> So you don't need a new media type.  I fully agree with DanC's
> assessment here;
> http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0162.html

Don't see how that helps with OWL. Quite the contrary.

>>>> Now, the sender _may_ be wanting you to think "Yea, verily, this
>>>> information is true, and I _am_ expecting everyone to apply RDF
>>>> interpretation rules to it", but there are many other possibilities.
>>> Yup.
>> Hence you can't infer things *either way*. I.e., you can't assume that
>> the sender *didn't* want her text/plain to communicate the graph.
> I don't see how that follows.  Perhaps I misunderstood Thomas.
> I understood "possibilities" to mean possibilities for processing.
> If he meant possibilities for interpretation of semantics,

How can you separate the two?

>  then I
> disagree.  Ambiguity in message semantics is really bad thing.


>> Mimetypes don't tell use a lot about content, actually. Imagine a gif
>> of an rdf graph. That might well communicate the graph! Why not? 
>> (e.g.,
>> I have an ocr program)
> If we're just talking about automata here, then no, the graph is not
> communicated, because the recipient can't "follow your nose" from any
> information in the message to any specification which says the graph is
> being communicated.

I wasn't aware that automata had noses to follow.

Nose following, in any case, isn't the only way.

>  You either need a new media type (image/rdf+gif?)
> or out-of-band agreement between the parties for that to happen.


> But
> for an Internet scale system like the Web, I consider the latter a
> non-starter.

So we disagree.

There's also an Always/Usually issue. I think that Usually is fine, but 
once you say Always then you've made your system way way way too rigid. 
It's very hard to capture all the different implicit and explicit 
agreements and understandings people come up with (sanely) and encode 
in their programs. Hamfisting it just makes people either ignore your 
restrictions or not use your system.

Bijan Parsia.
Received on Friday, 26 March 2004 13:06:36 UTC

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