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Re: Importing RIF documents from RDF - last attempt

From: Jos de Bruijn <jos.debruijn@gmail.com>
Date: Thu, 18 Mar 2010 17:01:38 +0100
Message-ID: <4BA24E62.2050900@gmail.com>
To: Axel Polleres <axel.polleres@deri.org>
CC: Chris Welty <cawelty@gmail.com>, RIF <public-rif-wg@w3.org>, Ivan Herman <ivan@w3.org>, Birte Glimm <birte.glimm@comlab.ox.ac.uk>, Chimezie Ogbuji <ogbujic@ccf.org>, Sandro Hawke <sandro@w3.org>
I see what you mean. An implementation that does not take one of the
imports into account does not follow the spec.

Now, concerning the rif:imports. Could you explain me again why it is a
good idea to extend the RDF semantics to include RIF-RDF combinations?
I understand that you want to use SPARQL to query RIF-RDF combinations.
How does the syntactic construct in RDF help? Why not have implicit
rulesets (like the implicit datasets) and give the user the possibility
to refer to a RIF ruleset from the query?

Jos

On 2010-03-18 11:18, Axel Polleres wrote:
>> I'm not sure what you mean with the imports mechanism having a
>> semantics. The semantics of the combination (R2,G) is clearly defined in
>> the SWC spec.
> 
> Yes it is clearly defined, and it wouldn't take the import of R1 from G 
> into account. So, in case we define a semantics for importing rulesets 
> from graphs, an implementation that takes this imports-mechanism into 
> account will not be compatible to the SWC spec on this example.
> 
> Axel
> 
> On 18 Mar 2010, at 10:10, Jos de Bruijn wrote:
> 
>>
>>
>> On 2010-03-12 15:32, Axel Polleres wrote:
>>> On 12 Mar 2010, at 14:09, Chris Welty wrote:
>>>> Axel,
>>>>
>>>> I really really really do not understand why it matters whether RIF specifies this or SPARQL.
>>>> RIF should be viewed as read-only right now unless there is an error.
>>>
>>> 1) the *main issue* is the URI we use for dereferencing, which we think should be in the rif: namespace, i.e. we need
>>>    rif:'s blessing if we do so.
>>>
>>>
>>> I mentioned in the mail already that it would probably be an alternative if we could just produce a (joint?)
>>> note or separate (rec?) document on this. That would mean we wouldn't touch the rif-rdf-owl spec as such. However ...
>>>
>>> 2) ... as I see it there is *potential issue* around a separate spec which worries me a lot...
>>> if we *don't* specify the importing from RDF within rif-rdf-owl, then whatever we write in that note separate spec
>>> would be potentially incompatible with rif-rdf-owl ... here's why:
>>>
>>> Say you have two rulesets R1, R2 and one graph G:
>>>
>>>   G:
>>>      G <> rif:imports [rif:ruleset R1 rif:profile <...simple...> ].
>>>
>>>   R2:
>>>     Imports( G <...simple...> )
>>>     ... some rules ...
>>>
>>>   R1:
>>>     (Imports R2)
>>>     ... some other rules ... no imports clause
>>>
>>> Now... depending on whether or not the imports-mechanism in RDF has a semantics, the RIF-RDF combination  (R2,G)
>>> has different semantics.
>>
>> I'm not sure what you mean with the imports mechanism having a
>> semantics. The semantics of the combination (R2,G) is clearly defined in
>> the SWC spec.
>>
>>
>> Cheers, Jos
>>
>>>
>>> So, my worry is, if we postpone that issue to post-RIF, we can't define it in an upwards compatible way at all...
>>> besides, I think it is a very minor change, which makes live much easier for applications coming from the RDF side
>>> doing something with RIF and doesn't seem to affect 99% of those caring from the RIF side only.
>>>
>>> Axel
>>>
>>>
>>>> -Chris
>>>>
>>>> Axel Polleres wrote:
>>>>> Hi all,
>>>>>
>>>>> We had the topic of "rif:imports" coming up in SPARQL again in our Entailment regimes taskforce call this week.
>>>>>
>>>>> The reason why we (from the SPARQL side) would prefer to have that imports mechanism defined in RIF,
>>>>> is mainly that we think that the URIs to use for defining this imports mechanism should be in  the rif:
>>>>> namespace, since this imports mechanism is likely useful not only for SPARQL but also for other
>>>>> RDF applications that wnat to interact with RIF.
>>>>>
>>>>> Thus, I wanted to inquire again, whether we'd have a chance to get that an import mechanism for RIF from RDF into
>>>>> http://www.w3.org/TR/rif-rdf-owl/ ?
>>>>>
>>>>> If the group overall still thinks that it is too late to get this into the spec, in turn, I wanted to ask/raise
>>>>> again how/whether we could proceed to publish this text as a WG Note?
>>>>>
>>>>> I have earlier made a simple proposal to add a new section to the current spec, which we elaborated a bit now:
>>>>>
>>>>> 1) In the introduction of http://www.w3.org/2005/rules/wiki/SWC,
>>>>> I would suggest to add:
>>>>>
>>>>> "RDF Graphs in RIF-RDF-combinations are assumed to not contain any triples using the predicates
>>>>> rif:imports, rif:ruleset and rif:profile we refer to Section 6 for treatment of such graphs.
>>>>> "
>>>>>
>>>>> 2) Further, I would suggest to add a new section:
>>>>> ====================================================================================
>>>>>
>>>>> = 6 Importing RIF rulesets in RDF =
>>>>>
>>>>> The definitions so far, only covered RIF-RDF-combinations where the RDF graphs did not contain
>>>>> triples using rif:usingRuleset in predicate positions. To lift this restriction, we define
>>>>> RIF-X-combinations (R,S) where any of the graphs in S contains triples with the predicates
>>>>> rif:imports, rif:ruleset and rif:profile
>>>>> by a reduction to combbinations without such triples as follows.
>>>>>
>>>>> Let (R, S) be a combination as above. The reduction of R is defined as the
>>>>> RIF-X-combinations (R', S') where
>>>>>  (i) S' is identical to S with all rif:imports, rif:ruleset and rif:profile triples removed,
>>>>>      and
>>>>>  (ii) R' is identical to the RIF document R,
>>>>>       with the addition that R' has additional imports clauses
>>>>>       Imports( R1 )
>>>>>       Imports( G P )
>>>>>      for any triples
>>>>>
>>>>>        <> rif:imports [rif:ruleset R rif:profile P ].
>>>>>
>>>>>      in (simple entailed by) S, such that R1 is an IRI referring to a RIF document and
>>>>>      P is a URI referring to an imports profile as defined in
>>>>>      Section http://www.w3.org/2005/rules/wiki/SWC#Profiles_of_Imports
>>>>>
>>>>> Together with the conditions in section 5.2 this ensures that RIF-X-combinations where R is empty, i.e. which
>>>>> are only defined by a set of RDF graphs, can also import RIF rulesets.
>>>>>
>>>>> ====================================================================================
>>>>>
>>>>> In case there is a chance to get this on one of the next agendas, please let me know, since I have recently not
>>>>> really had time to be follow the RIF TCs, but I'd be joining for that.
>>>>>
>>>>> best,
>>>>> Axel
>>>>>
>>>>> P.S.: Condition (i) which removes all the rif:usingruleSet triples, i.e.,
>>>>> just treats these triples as a directive rather than part of the graph, may be dropped, i.e. simply
>>>>> keeping S as is, accepting the rif:imports, rif:ruleset and rif:profile triples as part of the graph.
>>>>>
>>>>
>>>> --
>>>> Dr. Christopher A. Welty                    IBM Watson Research Center
>>>> +1.914.784.7055                             19 Skyline Dr.
>>>> cawelty@gmail.com                           Hawthorne, NY 10532
>>>> http://www.research.ibm.com/people/w/welty
>>>>
>>>
>>>
>>
>> --
>> Jos de Bruijn
>>   Web:          http://www.debruijn.net/
>>   LinkedIn:     http://it.linkedin.com/in/josdebruijn
>>   Skype:        josdebruijn
>>   Google Talk:  jos.debruijn@gmail.com
>>   Mobile phone: +43 660 313 5733
>>
> 

-- 
Jos de Bruijn
  Web:          http://www.debruijn.net/
  LinkedIn:     http://it.linkedin.com/in/josdebruijn
  Skype:        josdebruijn
  Google Talk:  jos.debruijn@gmail.com
  Mobile phone: +43 660 313 5733
Received on Thursday, 18 March 2010 16:02:13 GMT

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