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Re: concerning lite, fast, large versions of OWL

From: Christopher Welty <welty@us.ibm.com>
Date: Thu, 17 Oct 2002 08:11:13 -0400
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Cc: www-webont-wg@w3.org, www-webont-wg-request@w3.org
Message-ID: <OFF07EC57A.4E966382-ON85256C55.0041DBBC@pok.ibm.com>

This is a good summary, Frank.  I missed this discussion since I was in 
the wine group, and 
didn't hear it in the recap nor see it in the minutes.  Just be sure I was 
understood - I agree with 
Frank's points and think that a design accoring to:

OWL Light < OWL/FOL-style < OWL/RDF-style (1)

while certainly more complicated than having one or two language versions, 

is vastly preferable to a design that has:

OWL Light < OWL/RDF
OWL/FOL < OWL/RDF (2)

I find (1) to be quite compelling, and (2) to be a potential PR disaster, 
not to mention creating 
interoperability issues of the sort that OWL is supposed to solve!

Let's get this issue into the open and resolve it, before outsiders get 
wind that we have added
another language.

Dr. Christopher A. Welty, Knowledge Structures Group
IBM Watson Research Center, 19 Skyline Dr.
Hawthorne, NY  10532     USA 
Voice: +1 914.784.7055,  IBM T/L: 863.7055
Fax: +1 914.784.6078, Email: welty@us.ibm.com




Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Sent by: www-webont-wg-request@w3.org
10/17/2002 05:01 AM
Please respond to Frank van Harmelen

 
        To:     Christopher Welty/Watson/IBM@IBMUS, www-webont-wg@w3.org
        cc: 
        Subject:        Re: concerning lite, fast, large versions of OWL

 


Here we go again, I would almost say:-)

Large OWL (or: "OWL RDF-style") has classes as instances
  (any legal RDF combination of the constructs in the language is allowed,
   including "someclass type someclass)

Fast OWL (or: "OWL FOL-style") does not allow classes as instances
  (since this would go beyond the FOL framework)

Reasoners for OWL/RDF-style will be much harder to implement than 
reasoners 
for OWL/FOL-style (complete reasoners would be impossible to implement if 
OWL/RDF-style turns out to be an undecidable language, as it might well 
be)

In principle, we can decide to have OWL-Light "RDF style" (any 
RDF-combinations are allowed, include classes-as-instances), or we can 
decide 
to have OWL-Light "FOL style" (much more restricted).

Since OWL Light (still wanting a better name) should have ease of 
implementation as an important design criterion, it would make no sense to 

use the "RDF-style" for OWL Light, since this would make implementation of 

reasoners (and many other tools, e.g. editors, visualisers etc) much 
harder.

Furthermore, designing OWL light "FOL style" has the advantage that we 
have 
the following simple inclusion

                 OWL Light < OWL/FOL-style < OWL/RDF-style       (1)

both syntactically and semantically.
Allowing classes as instances in OWL Light would break this chain; another 

reason for not having them in OWL Light.

It is often somehow suggested, either explicitly or implicitly, that a 
design 
according to (1) is somehow complicated. I disagree. I find such a strict 
inclusion of languages easy to explain to people whom I explain OWL to
(and that is a wide range of people varying from CS undergrads to 
industrial 
programmers and managers).

View (1) was discussed at the F2F (when a number of people were in another 

meeting discussing wine ontologies); there was widespread agreement among 
the 
people present at that discussion that (1) was a much better option than 
including classes-as-instances in OWL Light.

Frank.
   ----

Christopher Welty wrote:

>
> Although I am strongly in favor of having "classes as instances" in some
> version of OWL, I am also very strongly in favor of as simple as 
possible
> a view of our language.
>
> Although consensus regarding the layering was a major accomplishment, it
> leaves us now with three versions of OWL: fast and large based on the 
RDF
> syntax/semantics, and of course the orthogonal "lite" version of the
> language.
>
> Having three versions of the language opens us up to some pretty obvious
> criticisms, in my view.  I think this would be even worse if OWL Lite,
> which is supposed to be a simplified version of OWL, is not a subset of
> Fast OWL, since Fast OWL is a subset of Large OWL.
>
> I was passionately ambivalent about OWL Lite in general, but I would
> strongly object to it as yet another subset of Large OWL.  Several 
people
> have expressed opinions that "classes as instances" should be in OWL 
Lite.
>  I'm not sure why - if it is allowed in Large OWL, then what difference
> does it make if it is in OWL Lite?
>
> -ChrisW
>
> Dr. Christopher A. Welty, Knowledge Structures Group
> IBM Watson Research Center, 19 Skyline Dr.
> Hawthorne, NY  10532     USA
> Voice: +1 914.784.7055,  IBM T/L: 863.7055
> Fax: +1 914.784.6078, Email: welty@us.ibm.com
>
Received on Thursday, 17 October 2002 08:11:56 GMT

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