Re: A summary of the proposal for resolving the issues with rdf:text --> Could you please check it one more time?

On Wed, May 20, 2009 at 08:04:50AM -0400, Alan Ruttenberg wrote:
> Hello Boris,
> 
> In what forum do you suggest this be addressed?

I suspect the answer would be RDF Core, except RDF Core doesn't exist
right now, so the questions of interop and fidelity to the RDF model
seem to land in the lap of the group whose users are likely to notice,
namely, SPARQL.

> -Alan
> 
> On Wed, May 20, 2009 at 7:38 AM, Boris Motik
> <boris.motik@comlab.ox.ac.uk> wrote:
> > Hello,
> >
> > I fully appreciate use case and I agree with your observation: this is something
> > that has to be addressed. I don't think, however, that solving this problem is
> > in the domain of rdf:text. The rdf:text specification merely defines yet another
> > datatype by specifying it in exactly the same way as this is done in XML Schema.
> > This datatype is just like any other XML Schema datatype; hence, the job from
> > rdf:text's point of view is done.
> >
> > Furthermore, the addition of rdf:text to the mix of the supported datatypes adds
> > no new conceptual problems to SPARQL: the situation with rdf:text is no
> > different than with, say, xsd:integer (there are other examples as well). For
> > example, assume that you have an RDF graph
> >
> > G = { <a, b, "1"^xsd:integer> }
> >
> > but you ask the query
> >
> > Q = { <a, b, "1.0"^^xsd:decimal> }.
> >
> > Clearly, G D-entails Q, so Q should be answered as TRUE in G. It is not the
> > business of XML Schema to specify how this is to be achieved: XML Schema merely
> > specifies what the correct answer to the above question is. It is a SPARQL
> > implementation such as OWLIM that should think of how to support such a
> > definition.
> >
> > I don't know whether a solution to the above problem (with xsd:integer and
> > xsd:decimal) exists. If not, I agree that one should be developed; however, we
> > would not go to the XML Schema WG and ask them to specify how should SPARQL
> > handle this case, would we?
> >
> > The problem with rdf:text is *precisely* the same as the one that I outlined
> > above. At an abstract level, it can be stated as "Several syntactic forms of
> > literals get mapped to the semantically identical data values". AS demonstrated
> > above, this problem exists without rdf:text, so I don't see how rdf:text brings
> > anything new into the whole picture. Thus, you can apply to the rdf:text case
> > exactly the same solution that you would apply to xsd:integer and xsd:decimal.
> > If such a solution doesn't exist yet, then the SPARQL WG should address these
> > issues, and it should do so in general for all datatypes (xsd:integer,
> > xsd:decimal, and so on), not just for rdf:text.
> >
> > To summarize, I think that the work from the point of view of the rdf:text WG is
> > *done* and that we should not do anything else in this forum.
> >
> > Regards,
> >
> >        Boris
> >
> >> -----Original Message-----
> >> From: Eric Prud'hommeaux [mailto:eric@w3.org]
> >> Sent: 20 May 2009 13:18
> >> To: Boris Motik
> >> Cc: 'Seaborne, Andy'; 'Alan Ruttenberg'; public-rdf-text@w3.org; 'Sandro
> >> Hawke'; 'Axel Polleres'
> >> Subject: Re: A summary of the proposal for resolving the issues with rdf:text
> >> --> Could you please check it one more time?
> >>
> >> On Wed, May 20, 2009 at 09:29:00AM +0200, Boris Motik wrote:
> >> > Hello,
> >> >
> >> > I don't see the benefit of option 1, as it makes things unnecessarily
> >> complex.
> >> > The fewer exceptions we have, the easier it will be to actually implement a
> >> > conformant system. The dichotomy between plain und typed literals is just an
> >> > example of an exception that just makes implementation difficult. Instead of
> >> > introducing more special cases, I think we should unify these whenever
> >> possible.
> >> >
> >> > Furthermore, I'm not sure whether sorting out things such as the ones
> >> pointed
> >> > out below is necessary to finalize the rdf:text specification. Please note
> >> that
> >> > rdf:text already has a well-defined lexical and value space, and this is
> >> *the
> >> > only* thing that we need to be able to plug rdf:text into the model theory
> >> of
> >> > RDF. That is, given RDF graphs G1 and G2 possibly containing rdf:text
> >> literals
> >> > and/or plain literals, using the definitions from the present rdf:text
> >> > specification one can unambiguously answer the question whether G1 D-entails
> >> G2.
> >> > For example, if G1 is
> >> >
> >> > <a, b, "abc@en"^^rdf:text>
> >> >
> >> > and G2 is
> >> >
> >> > <a, b, "abc"@en>
> >> >
> >> > then, according to the existing RDF model theory document, G1 D-entails G2
> >> and
> >> > vice versa. I don't see what else is there for the rdf:text specification to
> >> do:
> >> > I really think that the specification is complete. If SPARQL or other
> >> > specifications want to apply rdf:text in a different way and create special
> >> > cases, they are free to do so; however, I don't think it is in scope of the
> >> > rdf:text specification to solve all such problems.
> >>
> >> (Hesitantly re-stating use case), consider the use case of the OWLIM
> >> plugin for Sesame. If OWLIM forward chains some triples into the
> >> Sesame repository with objects like "bob"@en, existing SPARQL queries
> >> on the existing Sesame engine will match them as expected. RIF rules
> >> can consume those triples and know that any rules applying to a domain
> >> of rdf:text apply.
> >>
> >> Constrast that with an OWLIM which emits triples with objects like
> >> "bob@en"^^rdf:text . These triples will not match conventional queries
> >> intended to discover e.g. all the folks named "Bob". The Sesame SPARQL
> >> implementation can be extended, but then we are in Pat's scenario of
> >> fixing RDF by visiting all the deployed code.
> >>
> >> I expect that any design of rdf:text would have it reacting to plain
> >> literals as if they had a datatype of rdf:text and the appropriate
> >> lexical transformation. I propose that the simplest complete design is
> >> one where the inference of rdf:text objects results in their
> >> expression as plain literals, avoiding a dualism between
> >> "bob@en"^^rdf:text and "bob"@en which would lose interroperability
> >> with existing queries, graph APIs, XPaths operating on SPARQL Results,
> >> non-OWL inferencing systems, ...
> >>
> >>
> >> > Regards,
> >> >
> >> >     Boris
> >> >
> >> > > -----Original Message-----
> >> > > From: public-rdf-text-request@w3.org [mailto:public-rdf-text-
> >> request@w3.org]
> >> > > On Behalf Of Eric Prud'hommeaux
> >> > > Sent: 20 May 2009 03:18
> >> > > To: Seaborne, Andy
> >> > > Cc: Alan Ruttenberg; public-rdf-text@w3.org; Boris Motik; Sandro Hawke;
> >> Axel
> >> > > Polleres
> >> > > Subject: Re: A summary of the proposal for resolving the issues with
> >> rdf:text
> >> > > --> Could you please check it one more time?
> >> > >
> >> > > On Tue, May 19, 2009 at 03:57:11PM +0000, Seaborne, Andy wrote:
> >> > > > Apologies:
> >> > > >
> >> > > > > On Fri, May 15, 2009 at 11:50 AM, Seaborne, Andy
> >> <andy.seaborne@hp.com>
> >> > > wrote:
> >> > > > >> Monday PM end before 18:00 (GMT+1)
> >> > > > >> Thursday PM.
> >> > > > >> Tuesday @17:00 (GMT+1) for a short call; end before 17:30.
> >> > > >
> >> > > > I can't make the slot.
> >> > > >
> >> > > > Input: please consider interoperability of data between OWL and RDF.
> >> Option
> >> > > 1 is better for that than option 2 as Eric points out.
> >> > > >
> >> > > > This is also the least change to LC and IMHO is not a substantive change
> >> (it
> >> > > follows on from the current graph exchange intent) to add the text needed
> >> for
> >> > > SPARQL.  Roughly: the scoping graph of an rdf-text aware D-entailment for
> >> BGP
> >> > > matching includes the RDF forms and does not include ^^rdf:text.  (Non-
> >> aware
> >> > > entailment regimes would merely treat as a datatype form.)
> >> > >
> >> > > does anyone oppose option 1 (plain literals are considered to satisfy
> >> > > entailments constrained to type rdf:text and entailments of type rdf:text
> >> are
> >> > > expressed as plain literals in the RDF graph)? (i'm wondering if we can
> >> work
> >> > > this out before we work out scheduling this phone call.)
> >> > >
> >> > >
> >> > > >         Andy
> >> > > >
> >> > > > > -----Original Message-----
> >> > > > > From: Alan Ruttenberg [mailto:alanruttenberg@gmail.com]
> >> > > > > Sent: 19 May 2009 16:01
> >> > > > > To: Axel Polleres
> >> > > > > Cc: Seaborne, Andy; public-rdf-text@w3.org; Boris Motik; Sandro Hawke;
> >> > > > > eric@w3.orf
> >> > > > > Subject: Re: A summary of the proposal for resolving the issues with
> >> > > > > rdf:text --> Could you please check it one more time?
> >> > > > >
> >> > > > > On Mon, May 18, 2009 at 10:03 AM, Axel Polleres
> >> <axel.polleres@deri.org>
> >> > > > > wrote:
> >> > > > > > Alan, since you were calling for the TC, is that fixed now?
> >> > > > > > Otherwise, I am afraid it is not possible before Friday.
> >> > > > >
> >> > > > > Yes, let's have whoever can make it meet at 5:30 BST = 12:30 Boston
> >> > > > > time.
> >> > > > > Zakim, meet on irc #rdftext for the code. I will send a code earlier
> >> if
> >> > > > > I can.
> >> > > > >
> >> > > > > -Alan
> >> > >
> >>
> >>
> >> office: +1.617.258.5741 32-G528, MIT, Cambridge, MA 02144 USA
> >> mobile: +1.617.599.3509
> >>
> >> (eric@w3.org)
> >> Feel free to forward this message to any list for any purpose other than
> >> email address distribution.
> >
> >

-- 
-eric

office: +1.617.258.5741 32-G528, MIT, Cambridge, MA 02144 USA
mobile: +1.617.599.3509

(eric@w3.org)
Feel free to forward this message to any list for any purpose other than
email address distribution.