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Re: Distinguishing fragments

From: Jim Hendler <hendler@cs.rpi.edu>
Date: Fri, 7 Mar 2008 14:42:17 -0500
Cc: Web Ontology Language ((OWL)) Working Group WG <public-owl-wg@w3.org>
Message-Id: <B6806343-7B0C-49B3-9E08-9466F7708EBC@cs.rpi.edu>
To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>

Actually, the first message I sent was that I got some folks from the  
RDF community who surprised me because they didn't like our current  
fragments document, which I thought was pretty good.  THe primary  
questions they asked were as to what the reason was to have two DL  
fragments that seemed similar in many ways (OWL R DL and DL-Lite) and  
they suggested we drop one.  They also asked, if the idea was  
symmetry, why we would not have Full and DL versions of all the  
fragments - if it is useful to the "reasoning" community to have DL  
segments of these, why would it not be useful for the "RDF" community  
to have Full versions of the others -- after all, all of those would  
increase interoperability between the OWL and RDF worlds (their words,  
not mine).  I raised this off list with those who had volunteered to  
be on the fragments TF because I didn't want it to look like it was an  
attack on the document (which, again, I thought was pretty good).   
However, as at least a couple of the people I talked to were on the AC  
of the W3C, I thought it might be worth anticipating their comments  
and working them through.
  After several messages, which Ian has summed up below, modulo some  
minor changes (See inline)

On Mar 7, 2008, at 12:30 PM, Ian Horrocks wrote:

> We wanted to move a discussion on distinguishing fragments to the  
> list. Let me start by summarising what has been said so far (I used  
> my best endeavours, but others may want to add corrections/ 
> clarifications):
> Jim: why do we need a DL version of OWL-R? Couldn't it be confusing  
> with DL-Lite?
> Boris: OWL-R allows for moving between RDF and DL worlds -- may be  
> important to some.
> Jim: people I talked to said they would only use DL-Lite xor OWL-R
      this is DL-Lite XOR OWL-R DL (to clarify)
> Achille: Agrees that there is potential for confusion especially due  
> to fragment names; OWL-R DL covers datalog reasoning and colleagues  
> in China have a need for it.
> Boris: suggests OWL-T (taxonomic), OWL-R and OWL DB for EL++, DLP/ 
> rules and DL-Lite fragments.
> Jim: we would end up with the following naming scheme:
> OWL Full and OWL DL
> (OWL lite) - we hope to deprecate
> OWL-T Full
> OWL-DB Full
> OWL-R Full
> How would a user choose between OWL DB DL and OWL R DL? Thinks that  
> OWL-R and OWL-DB are both motivated by large scale data rich  
> applications, so would have a problem with the name OWL-DB for one  
> and not the other. Suggests OWL Datatlog and OWL Rules, but overlap  
> issue more important than names.
> Zhe: OWL-DB is confusing; Oracle has no short term plan to support;  
> suggests OWL-A (A for Abox) or OWL-I (I for instances) instead of  
> OWL-DB. Thinks OWL-R DL might be useful as a restricted version of  
> OWL-R Full.
> Jim: RDF triple store folks said they were confused about when to  
> use DL-Lite and when to use OWL-R DL. Suggest that it may be OK to  
> have asymmetric fragments (not always both Full and DL versions).
> Boris: OWL-R Full is for RDF users wanting more expressive power;  
> OWL-R DL is for OWL 1.1 DL users wanting to down-size. Nice thing is  
> that both communities can meet at the same level.
> Ian: Don't need symmetric fragments -- omit those with no clear  
> rationale (such as OWL-DB Full). Choosing between OWL-DB and OWL-R  
> should be easy: if you can live within the restrictions imposed by  
> OWL-DB and/or want to use data directly from relational DBs, then  
> use OWL-DB; otherwise, use OWL-R. Agrees that design issues more  
> important than naming.
> Ian: Can appeal to large community when they realise that they can  
> use OWL-DB with existing relational DBs. This isn't to detract from  
> OWL-R. Agrees with Achille that OWL-R DL can be be useful for LP  
> implementers.
> Ian: Need better names and a clear rationale (in fragments intro).  
> Case for "OWL-DB" is a no-brainer -- can use OWL directly with data  
> that is already sitting in relational DBs.
> Jim: asymmetry favours DL over Full?
> Jim: but why would we recommend to such users that they use OWL R DL  
> instead of DL-Lite?  Also if this is true of OWL R DL, why not DL- 
> Lite Full? Shall we move discussion to list?
> Ian: asymmetry means only including fragments for which there is  
> clear rationale.
> Ian: If users can't live within the restrictions imposed by DL-Lite  
> (it is quite a restricted language), then they should use OWL-R.  
> Yes, let's move to list.

"If we knew what we were doing, it wouldn't be called research, would  
it?." - Albert Einstein

Prof James Hendler				http://www.cs.rpi.edu/~hendler
Tetherless World Constellation Chair
Computer Science Dept
Rensselaer Polytechnic Institute, Troy NY 12180
Received on Friday, 7 March 2008 19:42:30 UTC

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