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Fragments discussion, continued

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Tue, 19 Feb 2008 10:27:29 -0500
Message-Id: <CEFF86FB-D70A-4DC4-9D14-627841E3644B@gmail.com>
To: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>

It seems (I hope) we are getting closer to some sort of mutual  
understanding of our needs for fragments. I'd like to sketch out the  
shape of what I'd be happy to see as an outcome of tomorrow's meeting.

I think we've heard convincing arguments that having a large number  
of fragments in Rec track, absent strong justification for each,  
isn't desirable. On the other hand, I'd like to put forward that  
there are compelling reasons to acknowledge OWL Lite, in the manner  
I've proposed, and to put 3 fragments on rec track, and proceed in  
subsequent meetings to nail down details of specification and  

The fragments:

1) OWL Prime (details of exactly what is in or out of OWL Prime  
remain to be worked out). Justified by specific industry interest  
from Oracle and HP, and to address the constituency that wishes to  
have a workable and more easily understandable rule-based OWL.
2) EL++. Justified by existing academic and commercial  
implementations, useful computational properties (polytime) and  
demonstrated use for working with important ontologies for  
biomedicine, a field which has been at the leading edge of Semantic  
Web adoption.
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.
This is probably DL-Lite, but I want to leave the door open to input  
from IBM, who's SHER implementation might also fit the bill. We  
haven't discussed this fragment much, so I'll give my view of why it  
is justified. 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.

To recap the OWL Lite proposal, the suggestion is to keep OWL Lite,  
unchanged, to support existing users, verify that it behaves as  
before using OWL 1.1 DL semantics, and write a Note to explain its  

Remaining fragments in the current Fragments document, would be  
described in one or more WG Notes.

My hope would be to not necessarily work out all the details  
tomorrow, but instead to come to agreement on this number of  
fragments (3) and their character, so that subsequent meetings  can  
be focused on implementation rather than policy.

Received on Tuesday, 19 February 2008 15:27:46 UTC

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