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Re: abstract class

From: Marc Carrion <marc_carrion@yahoo.es>
Date: Fri, 7 Feb 2003 01:42:48 -0800 (PST)
Message-ID: <20030207094248.36833.qmail@web11901.mail.yahoo.com>
To: pat hayes <phayes@ai.uwf.edu>
Cc: www-rdf-interest@w3.org

  Pat, if you don't mind I'm moving this thread to
interest list instead of comments list as Brian asked
us to do, because of the last call issue.

--- pat hayes <phayes@ai.uwf.edu> wrote:
> >--- Brian McBride <bwm@hplb.hpl.hp.com> wrote:
> >>  At 03:12 24/01/2003 -0800, Marc Carrion wrote:
> >>
> >>  [...]
> >>
> >>  >   That would be illegal if you don't have any
> >>  other
> >>  >information. But if you have had:
> >>  >     x rdf:type c .
> >>  >     c rdf:type rdfs:Abstract .
> >>  >     x rdf:type a .
> >>  >     a rdf:subClassOf c .
> >>  >   That would be correct.
> >>
> >>  Built into RDF is the assumption that any
> subgraph
> >>  of an RDF graph is a
> >>  legal RDF graph.  That's not likely to change
> >>  anytime soon.
> >>
> >    When using reification
> >      _:xxx rdf:type rdf:Statement .
> >      _:xxx rdf:subject <ex:a> .
> >      _:xxx rdf:predicate <ex:b> .
> >      _:xxx rdf:object <ex:c> .
> >    would be true, but if we only have
> >      _:xxx rdf:type rdf:Statement .
> >      _:xxx rdf:subject <ex:a> .
> >      _:xxx rdf:predicate <ex:b> .
> >    that would not be a 'correct' model, I mean
> it's
> >going to have a wrong Resource of type Statement.
> 
> No, not exactly. It is incomplete, not wrong. If I
> tell you that I
> have a head and two arms, you shouldn't conclude
> that I don't have
> any feet. The second graph *tells* you that _:xxx is
> of type
> Statement, so you (ought to) know that it *has* an
> object - they all
> do - but you just don't (yet) know what it is. RDF
> information is
> always potentially incomplete in this sense.

  Then, if I say
     _:xxx rdf:type rdf:Statement .
     _:xxx rdf:subject <ex:a> .
     _:xxx rdf:subject <ex:d> .
     _:xxx rdf:predicate <ex:b> .
     _:xxx rdf:object <ex:c> .
     _:xxx rdf:object "BLA" .

   Is that a wrong model? a incomplet model? At least
is an incorrenct rdf:Statement, isn't it?
> >
> >    The same when using Collections
> >      _:c1 rdf:type rdf:List .
> >      _:c1 rdf:rest _:c2
> >    which is a List without head, it's a correct
> Model
> >but an incorrect List

     _:c1 rdf:type rdf:List .
     _:c1 rdf:rest _:c2
     _:c1 rdf:rest _:c3
     _:c1 rdf:first "HEAD"
   And this should be an incorrenct List, it has to
rests.
 
> No, it is a list and you don't (yet) know what its
> head is. You know
> it is a list, however, since the first triple tells
> you it is.  RDF
> never gives you *definitions* in a strict sense, it
> only gives you
> *descriptions* (which might or might not be complete
> enough for you
> to figure out something you need to know, such as
> what the head of a
> list is.)

  Any way, we where thinking we should define abstract
classes in the same way

  _:x rdf:type _:ac
  _:c1 rdf:subClassOf _:ac
  _:c2 rdf:subClassOf _:ac
  _:ac rdf:type rdf:AbstractClass

  We were thinking this could be considered (or some
applications can consider it) as an incomplete model.
The think is you gain expressivity and it doesn't
imply too much work with the current model theory.
  
  Regards,
          Marc

> Pat Hayes
> 
> >
> >    I was thinking that Abstract Classes could be
> >defined in the same way.
> >
> >    Regards,
> >            Marc
> >
> >=====
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Received on Friday, 7 February 2003 04:42:50 GMT

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