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RE: Proposed response to Martin Merry, HP

From: Smith, Michael K <michael.smith@eds.com>
Date: Thu, 12 Jun 2003 09:41:35 -0500
Message-ID: <B8E84F4D9F65D411803500508BE3221416B16880@USPLM207>
To: Guus Schreiber <schreiber@cs.vu.nl>, Jim Hendler <hendler@cs.umd.edu>
Cc: www-webont-wg@w3.org

In response to Jims original message 

> 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?  

I have made the following change to the Guide.

  Ontology developers adopting OWL should consider which species best
  suits their needs.  The choice between OWL Lite and OWL DL 
  depends on the extent to which users require the more expressive
  restriction constructs provided by OWL DL.  
  Reasoners for OWL
  Lite will have desirable computational properties.  Reasoners for
  OWL DL, while dealing with a decidable sublanguage, will be subject to
  higher worst-case complexity. 

- Mike

Michael K. Smith, Ph.D., P.E.
EDS - Austin Innovation Centre
98 San Jacinto, #500
Austin, TX  78701

phone: +01-512-404-6683
email: michael.smith@eds.com

-----Original Message-----
From: Guus Schreiber [mailto:schreiber@cs.vu.nl] 
Sent: Wednesday, May 14, 2003 9:44 AM
To: Jim Hendler
Cc: www-webont-wg@w3.org
Subject: Re: Proposed response to Martin Merry, HP

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:

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.


> 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.
>> (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.
> [1] http://www.mindswap.org/papers/composition.pdf
> [2] http://www.cs.umd.edu/projects/plus/Parka/aaai97.ps
> [3] 


NOTE: new affiliation per April 1, 2003

Free University Amsterdam, Computer Science
De Boelelaan 1081a, 1081 HV Amsterdam, The Netherlands
Tel: +31 20 444 7739/7718
E-mail: schreiber@cs.vu.nl
Home page: http://www.cs.vu.nl/~guus/ [under construction]
Received on Thursday, 12 June 2003 10:42:08 UTC

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