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Re: The RDF Approach to Indicating Language-In-Use

From: Graham Klyne <GK@ninebynine.org>
Date: Thu, 06 Nov 2003 12:25:02 +0000
Message-Id: <>
To: Sandro Hawke <sandro@w3.org>, public-sw-meaning@w3.org

At 10:09 29/10/03 -0500, Sandro Hawke wrote:
>The question here (unless people want to stop and debate that
>finding), is how to achieve in RDF this functionality that mail and
>web systens achieve via Content-Type headers.  In RDF, we can't use
>header fields, unless we can figure out some way to have them survive
>a graph merge, which seems unlikely.  To rephrase: how is some
>software which is trying to act on information it receives as
>"application/rdf+xml", supposed to know whether it's looking at some
>OWL DL, some OWL Full, or some evil Anti-OWL where every URI means
>essentially the opposite of what it means in OWL Full?

This is an off-the-cuff response, made in ignorance of the follow-up 

It seems to me that the RDF/OWL-ish analogue to content-type labelling is 
class membership.  It operates at the resource level (as opposed to a 
"document" level), survives graph-merging, and can be used to sanction 
subsequent processing.  (Allowing, of course, that class membership can be 
inferred from the use of a property with known domain and/or range.)

I think some of Tim's work in CWM using (level-breaking?) properties like 
log:semantics may be indicative of this.  Hmm...
semantics       The semantics of a document is the formula acheived by 
parsing representation of the document. (Cwm knows how to go get a document 
and parse it in order to evaluate this.)
-- http://www.w3.org/2000/10/swap/doc/CwmBuiltins.html

Begs the question, *how* does CWM know how to parse the document?  Does it 
assume it's N3 or RDF/XML?

Ah, I see you later suggest something similar:

>I think Tim is suggesting that RDF should work just like mail and web
>content, except (1) using URIs instead of a central registry, (2)
>using every URI in the content as if it were, in essense, another
>content-type value.

But later:

>The second half of Tim's suggestion, if I understand it right, is that
>the language-in-use for an RDF graph be determined by a combination
>(conjunction/intersection, I guess) of the languages defined in all
>the specs the user/programmer/agent finds by dereferencing all the
>URIs in the graph.

Which seems to drag us back into the kind of regress that led us to throw 
out the "social meaning" elements of RDF.  I'll think some more about this.

>I do feel like something needs to be done beyond leaving it up to
>applications and subnets.  I imagine someone using owl:Class as a
>predicate relating people to an index of how "classy" a dresser they
>are .... and it seems like they are doing something wrong!  Yes, in
>that case, they are violating a W3C CR.  But what if they misuse
>dc:author as a synonym for rdf:type?  Even if you grant that W3C has
>some authority on correct use of RDF, does Dublin Core?  Or does the
>fact they they invented, published, and host that URL (the expansion
>of dc:author) actually count for something?

If a community of users decide to get together and do just this kind of 
"abuse", I can't see how we say it's invalid RDF.  And their applications 
might work just fine within their private walled garden.  Just not so well 
in the wider Internet.  It's this extra-logical notion of consensus again.


Graham Klyne
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Received on Thursday, 6 November 2003 09:12:30 UTC

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