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RE: Statements/Reified statements

From: Graham Klyne <GK@Dial.pipex.com>
Date: Tue, 28 Nov 2000 20:54:40 +0000
Message-Id: <4.3.2.7.2.20001128204850.00de7dc0@pop.dial.pipex.com>
To: Damien Morton <Morton@dennisinter.com>
Cc: www-rdf-interest@w3c.org
Personally, I tend to agree with you, but the RDF M&S currently uses 
rdf:_1, rdf:_2, etc.

However, the RDF M&S does not (cannot?) prevent one defining a different 
structure for describing ordered collections -- such as "link list" as you 
suggest (but beware: the "links" here are illusory --- don't think of them 
like C structures).  But be aware that that approach too will suffer from a 
requirement for re-writing if you wish to insert a new element (though not 
as many rewrites as the numbered property approach).

#g
--

At 11:45 AM 11/24/00 -0500, Damien Morton wrote:

>I recently subscribed to the RDF list, and have been doing my reading on RDF
>for a while now.
>
>I hope you will forgive me if I ask a question or two.
>
>If an rdf database contains a set (s,p,o) statements, how is ordering meant
>to be implemented?
>
>I see that the predicate rdf_n is used in rdf sequences, but surely when an
>object is inserted into a collection at some position, all of the rdf_n
>predicates will have to be renumbered to reflect the new ordering. Is my
>understanding correct? Isnt this something of an implementation nightmare,
>causing a single insertion or deletion to require re-stating of all of the
>membership statements about the collection.
>
>If one were to restate all of the membership statements, how would you query
>for "x: (container, rdf_n, ?x)", given that you dont know what n is, and
>that you probably dont want to be doing regular expression searches on
>predicates.
>
>Surely a better way would be to implement this as a linked list of
>statements.
>
>
>
> > -----Original Message-----
> > From: Bill de hÓra [mailto:dehora@acm.org]
> > Sent: Thursday, November 23, 2000 3:21 PM
> > To: www-rdf-interest@w3c.org
> > Subject: Re: Statements/Reified statements
> >
> >
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > : Bag <-type- A -rdf_1-> B           =        Bag <-type- A -rdf_1->
> > C
> > :               -rdf_2-> C                                  -rdf_2->
> > B
> > :
> > : It makes sense to ask whether some resource is a member of a bag.
> > Does it make sense
> > : to ask a resource, to be the "second" member of a bag?
> >
> > No. A bag has no natural ordering. Containers use this notation to
> > identify members, it is a bit confusing but you get used to it. You
> > can call this an "artefact" of the model/xml.
> >
> > - -Bill de hÓra

------------
Graham Klyne
(GK@ACM.ORG)
Received on Wednesday, 29 November 2000 16:07:36 GMT

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