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Re: PRPOSAL to close ISSUE-8

From: Carsten Lutz <clu@tcs.inf.tu-dresden.de>
Date: Sat, 15 Dec 2007 10:19:47 +0100 (CET)
To: Alan Ruttenberg <alanruttenberg@gmail.com>
Cc: Uli Sattler <sattler@cs.man.ac.uk>, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, public-owl-wg@w3.org
Message-id: <Pine.LNX.4.64.0712151016400.24803@frege.inf.tu-dresden.de>

On Thu, 13 Dec 2007, Alan Ruttenberg wrote:
> On Dec 13, 2007, at 4:12 PM, Carsten Lutz wrote:
>> On Thu, 13 Dec 2007, Uli Sattler wrote:
>>> On 13 Dec 2007, at 16:04, Alan Ruttenberg wrote:
>>>> I have had a discussion with Uli about this, and it seems that a limited 
>>>> form of this would not compromise decidability - e.g. no binary 
>>>> comparisons other than equality. She said she would write up a proposal.
>>> ...I seem to remember that i agreed to have a think (!) about it - and I 
>>> had: it seems to me that (i) we would need to "fork" OWL11 in a difficult 
>>> to understand way (i.e., you can either use datatype properties at the end 
>>> of property chains or, say,  comparisons, but not both), and (ii) we would 
>>> need to ask implementors whether they would be willing to implement this. 
>>> I would thus favour to not allowing them at all....Carsten?
>> I basically agree with your assessment. Adding datatype properties at
>> the end of property chains (lets call this "datatype chains") is very
>> close to what is called "full concrete domain support" in
>>  http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0197.html
>> but with equality as the only binary comparison.
>> Even if we have both datatype chains and binary comparisons, reasoning
>> will stay decidable. However, this combination poses serious
>> challenges to the reasoner developers. I think we better avoid
>> it. Without binary comparisons, I assume that datatype chains are ok
>> from an implementation perspective. On the other hand, I believe that
>> forking OWL DL should be avoided at all costs.
> This assessment is one, I think, that would need to be balanced against other 
> considerations. I don't understand the use of the word forking here. Again, 
> it seems a matter of degree, not kind when compared to existing constructs. 
> So I see your preference as one of taste, and that's why I think it needs to 
> be balanced with other considerations.

I think when Uli said forking, she meant having two different maximal
version of OWL DL. But you are right, this would not be necessary. 
there could be one version with appropriate non-structural restrictions
(such as "don't use a datatype role both in a datatype chain and an
n-ary comparison). On the other hand, I believe that we should also 
be very careful with those, for otherwise we are in danger of ending
up with a large number of such restrictions and with a very difficult
to understand standard. Yes, that is a personal opinion, just like 
the one one "forking".


*      Carsten Lutz, Institut f"ur Theoretische Informatik, TU Dresden       *
*     Office phone:++49 351 46339171   mailto:lutz@tcs.inf.tu-dresden.de     *
Received on Saturday, 15 December 2007 09:20:07 UTC

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