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

From: Jim Hendler <hendler@cs.rpi.edu>
Date: Thu, 6 Mar 2008 19:27:20 -0500
Cc: Bijan Parsia <bparsia@cs.man.ac.uk>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
Message-Id: <DA046A34-F827-4C9B-B29E-B96141988180@cs.rpi.edu>
To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>

Ahh, I misunderstood - I think we need to be very clear on this - I  
think some of us were assuming that the idea of the DB fragment was to  
be able to represent something close to a DB schema and use it in  
processing data from the DB (a la datalog/SQL type stuff) - sort of  
like expressing an E/R model and then using it to make simple  
inferences over the data.  Anyway, a lot of the project will be  
correctly describing these fragments and their features.
  -JH



On Mar 6, 2008, at 6:26 PM, Ian Horrocks 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
>
>
> 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
>>
>>
>>
>>
>>
>

"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 00:27:55 GMT

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