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Re: shared bnodes (Re: RDF dataset semantics again)

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 28 Aug 2012 17:55:33 +0100
Message-ID: <503CF805.2080804@epimorphics.com>
To: public-rdf-wg@w3.org


On 28/08/12 16:49, Steve Harris wrote:
>> If you don't have a syntax or protocol (such as an RDF API) for constructing graphs with shared bnodes, then, yes, you need to indicate that some kind of unification is desired/appropriate.
>> >
>> >It seems to me the simple. obvious, and appropriate way to handle this for most use cases is to allow blank node labels to be shared between different parts of a multi-graph document.
> It's very easy in the case where you want to indicate that the bNodes are shared - but there is some cost to it - when you want to produce the multi-graph document you need to ensure that the labels for distinct bNodes are kept distinct.
>
> Consequently you can't do tricks like:
>
> ( for i in *.ttl; do echo "<$i> {" ; cat $i ; echo "}" ; done ) > foo.trig
>
> I've never done anything exactly like that, and I have no feel for
> how  common a usecase it is, but it's worth noting that in RDF-2004 it would
> be "safe", and in RDF 1.1 it might result in shared bNodes, depending on
> how lucky you were.

@prefixes ?

	Andy

>
> I'm also not sure what existing practice is when reading multi-graph documents with shared bNode labels in different graphs. Certainly 4store creates different bNodes for each <label,graph> combination, as this is what RDF semantics says/said.
>
>> >An alternative would be to somehow use our Skolemization URIs, but that seems much more awkward.
Received on Tuesday, 28 August 2012 16:56:05 UTC

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