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Re: Importing RIF documents from RDF - last attempt

From: Axel Polleres <axel.polleres@deri.org>
Date: Fri, 12 Mar 2010 14:32:31 +0000
Cc: "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: <818D9E50-C31A-4B7D-AEA5-AFA7282F2271@deri.org>
To: "Chris Welty" <cawelty@gmail.com>
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.

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
> 
Received on Friday, 12 March 2010 14:33:07 GMT

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