W3C home > Mailing lists > Public > public-rif-wg@w3.org > March 2010

Re: Importing RIF documents from RDF - last attempt

From: Axel Polleres <axel.polleres@deri.org>
Date: Thu, 18 Mar 2010 10:18:43 +0000
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>
Message-Id: <D8E880AA-5076-4B85-9508-EA0F1E8120BC@deri.org>
To: Jos de Bruijn <jos.debruijn@gmail.com>
> 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
> 
Received on Thursday, 18 March 2010 10:19:21 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 18 March 2010 10:19:21 GMT