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Re: A possible way of going forward with OWL-R unification (ISSUE-131)

From: Ivan Herman <ivan@w3.org>
Date: Sun, 13 Jul 2008 17:00:12 +0200
Message-ID: <487A187C.4070509@w3.org>
To: Boris Motik <boris.motik@comlab.ox.ac.uk>
CC: public-owl-wg@w3.org
Hi Boris,

Boris Motik wrote:
> Hello Ivan,
> 
> I see many advantages to the proposed unification of OWL-R:
> 
> - Having only one OWL-R profile should be less confusing for implementers and users.
> 

Just as I said in my previous mail: I do not think this is not true for
OWL-R Full users and implementers. My belief is that for that crowd the
situation would be _more_ confusing than it is today.

> - An OWL-R implementation can also claim to handle OWL Full (although without the completeness guarantees).
> 

But this is exactly the muddy message I was referring to, isn't it? It
does not really implement OWL Full. If there is no clear reference to a 
name/profile, then it just not clear what it implements, except for a 
vague statement on incompleteness. That is certainly not what a company 
would put in a marketing brochure! By clearly identifying a subset of 
OWL-Full through the rule set, giving it a standard name as a profile, 
the situation becomes clear for all parties involved.

Actually, I am not even sure that your statement is correct. There is
nothing that would prevent an OWL-R-DL implementation to use other
implementation techniques, relying on the DL restrictions. In  which
case your statement would probably not be true any more. I do not
believe the profile document says (or should say) that the rule set is
the _only_ implementation method for OWL-R-DL... Ie, such an 
non-rule-based implementation would have the right to _refuse_ an RDF 
Graph that other OWL-R implementations (based on the rules) could process.

> - The syntactic definition can be used to inform users whether or not these guarantees hold for a given ontology.
> 

Yes, true for the DL version but only for the DL version.

> - Implementations can support a larger fragment of OWL Full without becoming incorrect for OWL-R.
> 

I am not sure I understand this statement

> - An OWL Full implementation *is* an OWL-R implementation.
> 

Of course. Just as a OWL DL is also an OWL-R-DL implementation. But this
statement is irrelevant in the context of profiles...

> - No need for owl:intendedProfile.
> 
> Under the current profile definition, if implementers add functionality beyond OWL-R, as they might want to do, then their
> implementation would be strictly speaking incorrect for OWL-R Full.
> 

I am not sure I understand the relevance of this...

The other day I asked you on the call whether, by accepting your 
proposal, we would loose anything. You said the answer is 'no' but, 
unfortunately, my examples show that this is not exactly true. We 
probably have a different appreciation on the importance of those things 
that we do loose... in other words, we can just agree at this point that 
we disagree:-(

Ivan


> Regards,
> 
> 	Boris
> 
> 
>> -----Original Message-----
>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Ivan Herman
>> Sent: 12 July 2008 09:47
>> To: Boris Motik
>> Cc: public-owl-wg@w3.org
>> Subject: Re: A possible way of going forward with OWL-R unification (ISSUE-131)
>>
>> Hi Boris,
>>
>> I must admit I do feel a bit uncomfortable with this. My unease is not
>> on the technical aspect but more on the 'messaging' side.
>>
>> What the proposal amounts to is to say that if I am an RDF user who uses
>> OWL-R, and I happen to use, say, the RDF List vocabulary, then I am not
>> in any official profile of OWL in spite of the fact that the rule set of
>> OWL-R work perfectly well. On the other hand, if I do not use the List
>> vocabulary then I am ok. For an RDF+OWL-R user this restriction may seem
>> fairly arbitrary.
>>
>> For vendors announcements it would look at bit unclear, too. What would
>> they announce as part of their product description? That they implement
>> OWL-R? But would that mean that, strictly speaking, they should reject
>> an RDF Graph using the List vocabulary? If they don't reject those then,
>> in fact, they do not implement OWL-R but an unnamed, unofficial, though
>> well defined OWL profile. With the current setup they could clearly
>> announce that what they implement is OWL-R-Full which is then well
>> referenced and defined.
>>
>> I wonder whether the advantages you describe below outweigh the
>> disadvantages of not having a clear reference to a profile that both
>> users and vendors can refer to. I have my doubts.
>>
>> Ivan
>>
>> Boris Motik wrote:
>>> Hello,
>>>
>>> Yes, some RDF Graphs will be syntactically outside the OWL-R fragment. The rules can still operate
>> on such graphs, but this might
>>> result in missing consequences that would be intuitively expected; in this case it can be seen as
>> an incomplete implementation of
>>> OWL Full. Advantages include streamlining the definition of OWL-R, making profiles in general much
>> cleaner and easier to understand,
>>> and obviating the need for owl:intendedProfile.
>>>
>>> Regards,
>>>
>>> 	Boris
>>>
>>>> -----Original Message-----
>>>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Ivan Herman
>>>> Sent: 11 July 2008 11:43
>>>> To: Boris Motik
>>>> Cc: public-owl-wg@w3.org
>>>> Subject: Re: A possible way of going forward with OWL-R unification (ISSUE-131)
>>>>
>>>> Boris,
>>>>
>>>> I do not see how this answers the questions I had in
>>>>
>>>> http://lists.w3.org/Archives/Public/public-owl-wg/2008Jul/0093.html
>>>>
>>>> Isn't it correct that this approach will make some RDF Graphs formally
>>>> incorrect OWL-R graphs (even if the rules can handle them without any
>>>> problems)?
>>>>
>>>> Ivan
>>>>
>>>> Boris Motik wrote:
>>>>> Hello,
>>>>>
>>>>> Here is a possible way of going forward with ISSUE-131.
>>>>>
>>>>> - We add to the introduction of the Profiles document a definition of what it means for an RDF
>>>> graph G to be an instance of profile
>>>>> P:
>>>>>
>>>>> "Let G be an RDF graph closed w.r.t. imports. G is a P-ontology if the triples in G can be parsed
>>>> into an ontology in structural
>>>>> specification that satisfies the grammar given in the profile specification for P".
>>>>>
>>>>> - We change Section 4 to talk only about OWL-R, and not about OWL-R DL and OWL-R Full.
>>>>>
>>>>> - We rename Section 4.2 to "Profile Specification".
>>>>>
>>>>> - We delete Section 4.3.1.
>>>>>
>>>>> - We rename Section 4.3.2 into Section 4.3 and call it "Reasoning in OWL-R and RDF Graphs using
>>>> Rules".
>>>>> - In current Section 4.4, we already have a statement that, for OWL-R ontologies, describes the
>>>> consequences that these rules
>>>>> produce. In the end of this section, however, we would add the following sentence:
>>>>>
>>>>> "The rules from Section 4.3 can be applied to arbitrary RDF graphs, in which case the produced
>>>> consequences are sound but not
>>>>> necessarily complete."
>>>>>
>>>>> Please let me know how you feel about this.
>>>>>
>>>>> Regards,
>>>>>
>>>>> 	Boris
>>>>>
>>>>>
>>>> --
>>>>
>>>> Ivan Herman, W3C Semantic Web Activity Lead
>>>> Home: http://www.w3.org/People/Ivan/
>>>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>>>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>>
>> --
>>
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Sunday, 13 July 2008 15:00:47 UTC

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