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RE: What is it that's wrong with rdf:List

From: Michael Schneider <schneid@fzi.de>
Date: Fri, 18 Jun 2010 23:49:35 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A001E9A5AD@judith.fzi.de>
To: "Sandro Hawke" <sandro@w3.org>
Cc: "Paul Gearon" <gearon@ieee.org>, "Semantic Web" <semantic-web@w3.org>, "Norman Gray" <norman@astro.gla.ac.uk>
Hi Sandro!

>-----Original Message-----
>From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org]
>On Behalf Of Sandro Hawke
>Sent: Friday, June 18, 2010 7:22 PM
>To: Michael Schneider
>Cc: Paul Gearon; Semantic Web; Norman Gray
>Subject: RE: What is it that's wrong with rdf:List
>
>On Fri, 2010-06-18 at 10:38 +0200, Michael Schneider wrote:
>> Paul Gearon wrote:
>>
>> >I haven't looked at your references yet, but both OWL Lite and OWL DL
>> >have constructs in them that are expressed in RDF using a list. So
>> >using a list does not force a model to become OWL Full.
>>
>> OWL DL (and OWL Lite) does /not/ allow the use of RDF lists as
>/semantic
>> entities/, that is, you cannot use lists in statements like
>>
>>     ex:journey ex:visitedCities ( ex:Berlin ex:London ex:Paris ) .
>>
>> OWL DL uses RDF lists as part of the RDF encoding of its syntactic
>> constructs. For example, an intersection of classes is encoded by
>something
>> like
>>
>>     _:x rdf:type owl:Class .
>>     _:x owl:intersectionOf ( :c1 :c2 ) .
>>
>> So lists may only occur in these well-defined contexts. Every other
>use of
>> RDF lists is disallowed in OWL DL.
>
>This is such a bug in OWL DL.   :-(    I think I keep blotting it from
>my memory, it's so painful.
>
>As part of that, I don't remember any discussion of this in the OWL
>Working Group. 

It was an official Working Group issue:

  <http://www.w3.org/2007/OWL/tracker/issues/129>

And there was quite some discussion (follow the thread being referenced
there). Strangely, I cannot find the really interesting part of the
discussion anymore (the thread suddenly stops). I believe to remember that
there were issues with the reverse RDF mapping. I think, it was at least
completely unclear how to get the reverse mapping right with lists as
non-syntax components. I don't remember the details anymore, though.

>Michael, do you have any idea how hard this would be to
>fix?  

See above.

>Naively, it seems to me like the OWL Functional Syntax could be
>extracted using the RDF list vocabulary when it's appropriate (eg as the
>object of owl:intersectionOf), and the other RDF List triples could be
>treated as normal data.

As long as one keeps within the Functional Syntax (or in the Structural
Specification), there should hardly be an issue, I guess, since in the
Functional Syntax, RDF Lists play no role. They are only relevant in the RDF
serialization. But keeping in the Functional Syntax and not moving to RDF
is, erm, not so typical for OWL usage, or? :-)

Best,
Michael

>To rephrase: OWL could use/restrict owl:first/owl:rest/owl:nil and for
>backward compatibility it could convert between these and the rdf:
>versions for its own syntactic structures.
>
>Maybe there's a concern about someone making a subproperty of rdf:first
>or something, but some counter-intuitive behavior if someone does that
>seems like a paltry concern compared to what we have now.
>
>   -- Sandro

--
Dipl.-Inform. Michael Schneider
Research Scientist, Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider

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Received on Friday, 18 June 2010 21:50:11 GMT

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