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Re: Klyne Contexts: 3. Statements sets in RDF

From: Graham Klyne <GK@Dial.pipex.com>
Date: Mon, 01 Jan 2001 17:50:35 +0000
Message-Id: <4.3.2.7.2.20010101174212.00e29610@pop.dial.pipex.com>
To: Jonas Liljegren <jonas@rit.se>
Cc: RDF interest group <www-rdf-interest@w3.org>, Wraf development <rdf@uxn.nu>
At 12:36 AM 12/29/00 +0100, Jonas Liljegren wrote:
>Graham Klyne <GK@Dial.pipex.com> writes:
>
> > It seems to me that, given an RDF graph, I should be able to extract
> > an arbitrary subgraph (i.e. a subset of the statements) and still have
> > a valid RDF graph.  The RDF approach to containers doesn't permit
> > this, because (I think) the following is not valid per RDF M&S:
> >
> >     [Foo] --rdf:type--> [rdf:Bag]
> >     [   ] --rdf:_1----> [Member1]
> >     [   ] --rdf:_3----> [Member3]
>
>I say that it must be valid.  I would even allow:
>
>      [Foo] --rdf:type--> [rdf:Bag]
>      [   ] --rdf:_1----> [Member1]
>      [   ] --rdf:_1----> [OtherMember1]
>      [   ] --rdf:_3----> [Member3]
>
>
>This because anyone can say anything about everything.

Look at RDF M&S, send of section 5.  It states that the ordinal properties 
must be used sequentially starting with rdf:_1.

This is why I think RDFM&S collections are broken when, as you say, "anyone 
can say anything about everything".

>Nobody can stop me if I feel like renumbering the properties of a
>bag.  But it should be clear that the new statements is not the
>original ones.

True, but I think that introduces horrible scalability problems for 
web-wide collation of information.

> > >1. With special methods for conatiner handling, you will not have to
> > >    bother about the present content.  Wraf will give each container
> > >    the dynamic property 'size', and methods for adding and quering the
> > >    container without knowing each propertys number.
> >
> > This assumes that your implementation knows about all of the members.
> > I think that's a kind of closed-world view.
>
>No. The size statement has a source.  Other sources can have another
>idea about the size of the container.  The statement will belong to a
>model and that model will have data about the scope of the known world.

My biggest objection to all this is that I believe all this extra logic is 
simply unnecessary.  It is possible to use base RDF to define container 
structures that just don't have these problems.  If you want to add extra 
structures to facilitate your own internal processing then that should be 
your choice as an implementer, not something that has to be done to 
overcome problems with the standard container structures.

#g


------------
Graham Klyne
(GK@ACM.ORG)
Received on Monday, 1 January 2001 14:00:47 GMT

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