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Re: PRPOSAL to close ISSUE-8

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Thu, 13 Dec 2007 19:07:21 -0500
Message-Id: <05E1AEBB-DE95-4C9D-85AE-1A5016A002D3@gmail.com>
Cc: Uli Sattler <sattler@cs.man.ac.uk>, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, public-owl-wg@w3.org
To: Carsten Lutz <clu@tcs.inf.tu-dresden.de>

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.

> BTW, I disagree with Alan that there are not many use cases for
> comparisons. For example, Sebastian gave many (and convincing ones) at
> the F2F. Uli, didn't he also send a mail with some use cases?

I see Mike's email and I am convinced, and happy.  I do note that  
none of cases have string comparisons, and that the use case  
presented for datatype chains was for strings. This presents another  
opportunity for supporting the feature (support datatype chains for  
string datatypes only). To ask for otherwise, I would say the onus  
would be on the part of comparison supporters to provide additional  
use cases motivating support for strings, or the datatype chain  
supporters motivating cases for other than strings. Modulo the  
"taste" issue, which I would rather not debate at the moment.

-Alan



>
> greetings,
> 		Carsten
>
>
>> Cheers, Uli
>>
>>> -Alan
>>> On Dec 13, 2007, at 9:56 AM, Peter F. Patel-Schneider wrote:
>>>> Issue-8 asks for property chains that end with data properties.
>>>> Adding this construct to OWL 1.1 would compromise decidability.
>>>> This feature would automatically be in an OWL Full version  
>>>> because in
>>>> OWL Full data properties are also object properties.
>>>> Later discussion asked whether having data properties in the  
>>>> middle of
>>>> a chain can be done.
>>>> In OWL 1.1 such chains would have an empty extension, and thus be
>>>> useless.  The situation in OWL Full is the same as for data  
>>>> properties
>>>> at the end of a chain.
>>>> I therefore propose that we CLOSE ISSUE-8 (even though it is not  
>>>> even
>>>> OPEN) without doing anything on the twin grounds that it both
>>>> compromises decidability in OWL 1.1 and is not handled by tools,  
>>>> and
>>>> that there is nothing special that needs to be done in OWL Full.
>>>> Peter F. Patel-Schneider
>>>> Bell Labs Research
>>>> PS: I'm proposing handling ISSUE-8 in this manner as is it is  
>>>> closely
>>>>    related to ISSUE-83.
>>
>>
>
> --
> *      Carsten Lutz, Institut f"ur Theoretische Informatik, TU  
> Dresden       *
> *     Office phone:++49 351 46339171   mailto:lutz@tcs.inf.tu- 
> dresden.de     *
Received on Friday, 14 December 2007 00:07:32 GMT

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