Re: concerning lite, fast, large versions of OWL

I have a few with respect to this issue:

1 - From a presentation perspective, I strongly prefer to have the inclusion 
relationship:
             Owl Lite < FastOwl < OWL

2 - I have heard some statements that OWL Lite is on the edge of not being 
lite enough.  Since I think this is a fair concern,  I am a bit more careful 
now about adding new features.  Adding classes as instances has the 
unpleasant side effect of breaking 1 above so i would be less inclined to 
look at this over other important features that are out of owl lite if I am 
looking to include a tiny bit more.

3 - there is nothing that says that there could not be another OWL dialect 
later.  If it turns out that OWL Lite plus classes as instances is a 
particularly useful dialect, it could be added as another dialect later after 
we make our initial announcement.
I prefer not to muddy the waters now.

Deborah McGuinness
dlm@ksl.stanford.edu

In a message dated 10/17/2002 2:01:35 AM Pacific Daylight Time, 
Frank.van.Harmelen@cs.vu.nl writes:


> 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
> >
> 
>