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Re: comment on the fragment document: (inverse) functional and DL-Lite

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Fri, 7 Mar 2008 08:24:55 +0000
Message-Id: <B64D1350-B366-4192-9ED3-C43F8310E745@comlab.ox.ac.uk>
Cc: Jim Hendler <hendler@cs.rpi.edu>, Bijan Parsia <bparsia@cs.man.ac.uk>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
To: Sandro Hawke <sandro@w3.org>

I agree that this is very important and that we should say it more  
prominently. In fact we need to say something about the important  
features of *each* fragment. The introduction to the Fragments doc  
seems like the obvious place -- it is currently rather minimalist,  
but could be expanded.

Ian



On 7 Mar 2008, at 01:59, Sandro Hawke wrote:

>
>>> Actually, the primary idea of DL-Lite is that it has logspace data
>>> complexity, which means that query answering can be implemented  
>>> using
>>> standard (relational) DB technology. In particular, a conjunctive
>>> query against a DL-Lite ontology can be re-written as an SQL query
>>> against a relational DB containing instance data.
>>>
>>> Ian
>>
>> In what document can/should we say something like that?  I think it's
>> very important.  (I realize the first part is in  
>> Fragments_Proposal, but
>> not the practical/market angle of its relationship to SQL.)
>
> (replying to myself) Arg -- it more-or-less says that later in the
> document.  I just missed it, before.  :-(
>
> Still -- maybe in a UCR document? -- it would be nice to have a  
> guide to
> the fragments that can be understood by people who wont read sentences
> with "LOGSPACE", etc, in them.  That can wait, though, I suppose.
>
>     -- Sandro
>
>>      - Sandro
>>
>>
>>>
>>>
>>> On 6 Mar 2008, at 19:23, Jim Hendler wrote:
>>>
>>>>
>>>> I thought the primary idea of DL-Lite was that it would provide
>>>> primary database functionality -- how can it do that without keys?
>>>>
>>>>
>>>> On Mar 6, 2008, at 6:18 AM, Bijan Parsia wrote:
>>>>
>>>>>
>>>>> On 6 Mar 2008, at 11:04, Ivan Herman wrote:
>>>>>
>>>>>> Boris, Bernardo,
>>>>>>
>>>>>> I went through
>>>>>>
>>>>>> http://www.w3.org/2007/OWL/wiki/Fragments_Proposal
>>>>>>
>>>>>> again today. One thing that I may have missed: I tried to see if
>>>>>> I can use (inverse)functional properties for DL-Lite or not. I
>>>>>> did not find any reference to those neither in 3.1 nor in 3.2.
>>>>>> Again, I may have missed something...
>>>>>
>>>>> Let's see if I can discern from the text the situation. (As a test
>>>>> of the spec.)
>>>>>
>>>>> In section 3:
>>>>> 	http://www.w3.org/2007/OWL/wiki/Fragments_Proposal#DL-Lite
>>>>>
>>>>> 	"""Several variants of DL-Lite have been described in the
>>>>> literature. The variant presented here is called DL-LiteR since it
>>>>> allows for property inclusion axioms; it therefore contains the
>>>>> intersection between RDFS and OWL 1.1 DL. Other variants trade
>>>>> property inclusion axioms for functionality and inverse-
>>>>> functionality of object properties."""
>>>>>
>>>>> I think this is clear that functionality and inverse functionality
>>>>> of *object* properties are forbidden.
>>>>>
>>>>> Actually ,the rest of the sections are quiet about data properties
>>>>> altogether. Which would mean that data properties are forbidden in
>>>>> this variant. Which means that it's not really the intersection of
>>>>> RDFS and OWL 1.1 DL?
>>>>>
>>>>> I do think that if we make this DL Lite not have data properties,
>>>>> the text should call that out (e.g., in the list of missing
>>>>> features). OTOH, I think we should allow data properties ;) I
>>>>> would think it would be ok to trade datasubproperties for keys
>>>>> (from a user pov)...I don't know if that would be ok from the
>>>>> logic/impelmentation pov off the top of my had (while retaining
>>>>> object subproperties).
>>>>>
>>>>> Cheers,
>>>>> Bijan.
>>>>>
>>>>>
>>>>>
>>>>
>>>> "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 08:25:11 GMT

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