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Re: Layering the Semantic Web: Problems and Directions

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 21 Feb 2002 14:27:46 -0500
To: GK@NineByNine.org
Cc: www-webont-wg@w3.org, hendler@cs.umd.edu
Message-Id: <20020221142746N.pfps@research.bell-labs.com>
Comments on comments.  I'm not going to put up a new version (yet) as the
changes are all very small.

From: Graham Klyne <GK@NineByNine.org>
Subject: Layering the Semantic Web:  Problems and Directions
Date: Thu, 21 Feb 2002 16:05:32 +0000

[comments at begining and editorial suggestions throughout removed]

> And of the document itself...
> 
> Section 2, 2nd para:
> - isn't modularized syntax via XML schema also a syntactic underpinning?

There is mention of XML schema in this paragraph in a context where it is
mentioned as a syntactic underpinning.

> Section 3, 5th para:
> - I'm puzzled by this.  I don't regard XML as having any (widely 
> understood) semantics to be honoured.  What is meant by this?  (This idea 
> of XML semantics reappears later in the document.)

We mean the data model for XML.  This has been clarified.

> Section 5, intro:
> - I think it might be instructional to explore the minimum parts of RDF(S) 
> that need to be removed to avoid the paradoxes.

Yes, but that would require work and could require much work.

> Section 5.1, 7th para:
> - "and would provide more meaning for constructs from lower languages" 
> doesn't make sense to me.  I can imagine being able to do more things with 
> the meaning that is there, but don't see how more meaning can be created 
> for the lower constructs.

Changed to

and would extend the meaning for constructs from lower languages, 

The intent is to allow for things like discovering subClassOf
relationships based on, e.g., sameClassAs.

> Section 5.1, general:
> - What are the features of RDF(S) that make the extension approach 
> problematic (or:  what might be removed to make it less so?).  I'm 
> wondering if there are any small, otherwise inconsequential, changes that 
> would make this approach more attractive.

Again, this would require work, and maybe considerable work.  The problem
is that just when you think you have removed a source of complexity you
discover how to get it back again through some roundabout route.

> Section 5.2:
> - I'm afraid I really didn't understand what was being proposed here.  E.g. 
> the section is headed "same syntax, diverging semantics" but in its 
> penultimate paragraph talks about "define a frame syntax (sic) for OWL ... 
> behaves the same as the non-frame version ... different at the syntactical 
> level".  That sounds like divergent syntax rather than semantics.

Under investigation.

> Section 5.3:
> - I find it unclear to what extent this approach differs from section 5.1, 
> other than that some element of RDF(S) would not be recognized in OWL.  If 
> that element were suitably insignificant, the practical effect might be 
> similar to 5.1.  Especially if there were some way to automatically 
> recognize unsupported elements of RDF(S) and replace them with equivalent 
> supported elements (possible using the extended OWL syntax).

It is most likely that any significant (computational) benefit would
require considerable divergence from RDF(S).  One potential way, as
recently suggested, would be to segregate rdf:type.  This is a big change
to RDF(S).

> #g
> --

peter
Received on Thursday, 21 February 2002 14:29:40 GMT

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