W3C home > Mailing lists > Public > public-owl-wg@w3.org > March 2008

Re: Distinguishing fragments

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Mon, 10 Mar 2008 11:01:18 +0000
Message-ID: <47D514FE.2030703@hpl.hp.com>
To: Jim Hendler <hendler@cs.rpi.edu>
CC: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>

I think we need to be clear about "recommended" fragments with 
conformance labels which mean something, and other fragments that might 
be useful but the label is somewhat less formal.

In my view, full versions of DL fragments don't work accept informally 
... it's partly to do with the design rationales.


Jim Hendler wrote:
> 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 Monday, 10 March 2008 11:02:44 UTC

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