Re: Fragments discussion, continued

On Feb 21, 2008, at 10:07 AM, Jim Hendler wrote:

> Alan, can you explain who it is whose been asking for that fragment  
> (as separate from the Prime fragment) and what the distinguishing  
> property would be?

Hello Jim,

First, OWL Lite is not proposed as a Rec track fragment, so it isn't  
properly in this list. My proposal was to have that be a note, as an  
accommodation to existing users.

Regarding DL-Lite, I'm not sure I have more to add to what I've  
already said.

> 3) A fragment characterized by scalability to large numbers of  
> instances (not necessarily scalable tbox) , but with strong  
> guarantees with respect to completeness and consistency detection.
..
> Such a fragment  fills a hole that neither of two other fragments  
> fill, as It is likely that OWL Prime will not allow existentials  
> in  a rule head (following pD*), and EL++ is not as scalable.

> In addition DL-Lite is implementable in relational databases with  
> queries translatable to SQL. I have heard of two academic  
> implementations ("the italians" &  Jeff Pan) and a commercial  
> implementation - Clark and Parsia's, and the nature of the fragment  
> is such that it would be easily adoptable by relational database  
> providers.

> Finally, it is my judgement, as a user, that strong guarantees of  
> the ability to detect inconsistency and give complete answers bring  
> high value to science applications.

Note that these criteria have not been suggested as those that guide  
the design of OWL Prime. Should they turn out to be achievable, and  
there are implementations that show this, then I would, of course,  
reconsider, as I am more interested in the criteria than the  
fragment. DL-Lite is already sitting in this space with 3 independent  
implementations, so I naturally suggested it.

FWIW, I will be a customer for a fragment like (3) in parts of my  
work, but to be honest, I see all three as being tools that I could  
put to good use.

In my view, the argument for moving from 3 to 2 rec track fragments  
is not compelling, and will meet with resistance for  small gain. In  
the spirit of compromise, and in the interest of moving forward, I  
would prefer if we now focus on the work of answering the remaining  
questions we need to in order to sanity check and ensure ourselves  
that these fragments pass muster.  Of the 3 rec track fragments,  
there were significant and substantive questions about the details  
about the details OWL Prime, and DL-Lite. For OWL-Lite, we have some  
verification of the conditions that we set out.

Regards,
Alan