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Re: Proposed response to Martin Merry, HP

From: Guus Schreiber <schreiber@cs.vu.nl>
Date: Wed, 14 May 2003 16:44:17 +0200
Message-ID: <3EC25641.6010603@cs.vu.nl>
To: Jim Hendler <hendler@cs.umd.edu>
CC: www-webont-wg@w3.org

Jim Hendler wrote:
> (note - there is a suggestion to editors for some wording changes to Ref 
> and Guide in this message - it is before the section marked personal 
> opinion)
> 
> 
> At 8:44 AM +0300 5/14/03, Jeremy Carroll wrote:
> 
>> In
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html
>>
>> DanC:
>>
>>>  On closer examination of the comment, it seems
>>>  to be more about what goes in OWL DL than
>>>  what goes in OWL Lite.
>>
>>
>> And in ...
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0174.html
>> DanC:
>>
>>> Please help me find the relevant decisions
>>> and/or find evidence that those implementations
>>> pass some relevant tests and/or add an
>>> issue to the issues list.
>>
>>
>> In January, we agreed a definition of a "complete OWL DL consistency 
>> checker",
>> if we had evidence that such a thing existed, and/or that more than 
>> one would
>> exist in the future (and the WG was satisfied that they would be 
>> practically
>> usable, rather than essentially theoretical exercises) then we could 
>> respond
>> with a message that indicated that, and that we thought that that was
>> sufficient to justify the DL level.
>>
>> If we don't have such evidence then I agree with
>> http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html
>>
>> DanC:
>>
>>>  Mr. Merry's point, "We're concerned that OWL users should have their
>>>  expectations met when they use OWL compliant systems." seems well
>>>  made, no?
> 
> 
> 
> So let's set their expectations correctly -- we did try, by the way - in 
> Reference, section 8.2 we say:
> 
> In particular, the OWL DL restrictions allow the maximal subset of OWL 
> Full against which current research can assure that a decidable 
> reasoning procedure can exist for an OWL reasoner.
> 
> and in 8.3 we say
> 
> The limitations on OWL Lite place it in a lower complexity class than 
> OWL DL. This can have a positive impact on the efficiency of complete 
> reasoners for OWL Lite.
> 
> 
> In fact, my original response to Mr. Merry was going to be that we had 
> already addressed his comments and point out these quotes --- However, 
> his comments and a couple of others we received show that we haven't 
> made the difference clear ENOUGH in our documents.  (For example, in 
> section 1.2 we don't mention the computational issue).  I therefore 
> suggest that editing Ref and Guide to set expectations is the correct 
> solution - consistent w/WG decisions in the past.
> 
> 
> One we could fix ref, is to make it clear that the difference between 
> OWL Lite and OWL DL with respect to this computational issue is there.  
> For example, when we first introduce Lite in section 1.2 of ref we say:
> 
> OWL Lite is particularly targeted at tool builders, who want to support 
> OWL, but want to start with a relatively simple basic set of language 
> features.
> 
> instead of saying it is known to have a relatively efficient decision 
> procedure (and citing the literature).  Maybe simply adding a sentence 
> after the one I cite above that says
> 
> "In addition, OWL Lite is designed based to fit into a known 
> computational class that, while exponential, is lower than the 
> complexity of OWL DL [cite something]"
> 

I agree with this change.

Also, I think the sentence earlier in this section (1.2) on OWL DL needs 
to be changed (as Dan also pointed out). It currently says:

[[
The main reason for having the OWL DL sublanguage is that tool builders 
have developed powerful reasoning systems which support ontologies 
constrained by the restrictions required for OWL DL.
]]

This requires some form of not pointing to the issues discussed by Ian 
in his December message on complexity:
http://lists.w3.org/Archives/Public/www-webont-wg/2002Dec/0239.html

I wouldn't mind incorporating Ian's message in some (edited) form into 
Ref, e.g. as extended note, as a new Sec. 8.4 (probably my preference) 
or as appendix.

Guus

> I also think the "Species of OWL" section of the Guide is also less 
> clear than it could be, and might be wordsmithed to make the issue 
> clearer (for example, OWL Lite could say "Desirable computational 
> properties" and OWL DL could say "maximal decidable subset, although 
> subject to a higher worst-case complexity")
> 
> Guus, Mike S -- would making these edits be acceptable?   If so, I would 
> include in the response to Merry and to the other similar issues.
> 
> 
> 
> <PERSONAL OPINION>
> 
> 
>> (A danger is that if OWL DL is tainted then the whole OWL brand is 
>> tainted).
>>
>>> Jeremy
> 
> 
> What I would say would make OWL DL "tainted" would be to remove oneOf 
> and hasValue.  hasValue is used in about 10% of the ontologies in the 
> DAML ontology library, and oneOf, although not heavily used in that 
> library, is IMHO necessary for mapping existing sources into ontologies 
> --my group has used it in many cases where we have used either an XML 
> schema or a database schema as the basis of an ontology, especially in 
> our work with Web Service Composition [1].  I would also remind the 
> group that we actually had support in the WG to put hasValue in Lite, 
> but decided not to due to the computational issue.
> 
> I would argue strongly that it is better to explain things more clearly 
> in our documents than to change the language.  We spent a long time 
> developing a language that is well balanced for many considerations, and 
> I'd like to see if used in practice before we start cutting useful 
> features because of computational issues that may rarely or never arise 
> in real applications. For instance, PARKA-DB [2], still the fastest 
> ontology management system deployed to date, is in the same complexity 
> class as OWL DL, but somehow people don't seem to mind since it can 
> answer most useful queries in a few milliseconds against ontologies with 
> tens of thousands of classes - it has a worst case time that could be in 
> several minutes for the largest ontologies built yet - but that doesn't 
> seem to matter since after 5 seconds it asks the user if they want to 
> continue, and most people say "no" and reformulate the query...
> 
> Quoting one of our comment raisers, speaking about OWL:
> 
> At 11:43 PM -0400 5/9/03, Bijan Parsia wrote in [3]:
> 4) Get the damn thing out the door.
> 
> </PERSONAL OPINION>
> 
> 
> [1] http://www.mindswap.org/papers/composition.pdf
> [2] http://www.cs.umd.edu/projects/plus/Parka/aaai97.ps
> [3] 
> http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0069.html 
> 
> 

-- 
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Received on Wednesday, 14 May 2003 10:44:21 GMT

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