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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 11:10:12 +0100
Message-ID: <4BA1FC04.4020400@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>

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
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Received on Thursday, 18 March 2010 10:10:51 UTC

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