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Re: [call for comments] voiD 1.0

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 30 Jan 2009 15:04:14 +0000
Cc: Michael Hausenblas <michael.hausenblas@deri.org>, Linked Data community <public-lod@w3.org>, Semantic Web community <semantic-web@w3.org>
Message-Id: <CCB49DD3-18A7-4849-9049-805A9E712F32@cyganiak.de>
To: Peter Ansell <ansell.peter@gmail.com>

Peter,

On 29 Jan 2009, at 23:11, Peter Ansell wrote:
> What was the rationale behind having both void:target and the
> combination of void:subjectsTarget and void:objectsTarget?
>
> I would have thought that linksets would always be directed, otherwise
> it leaves you uncertain about whether you can actually find anything
> in one set or the triples are actually contained in the other dataset.
> At least with subjectsTarget you can always be sure that that dataset
> will contain the relevant triples.

Reiterating what others said: Containment of link triples in a  
dataset, and direction of the link statements, are two separate issues.

Containment (which dataset physically contains the triples, that is,  
where can I find them via resolving URIs or via SPARQL queries or  
dumps) is indicated via void:subset. The linkset is a subset of the  
dataset that contains the link triples.

Directionality of the statements (which dataset provides the subjects,  
and which the objects?) is an orthogonal question. Note that dataset A  
could contain links to B of the shape "a:foo dc:creator b:bar" or of  
the shape "b:bar dc:creator a:foo". SubjectsTarget and objectsTarget  
can be used to distinguish between them.

The superproperty void:target was included for cases where we want to  
specify less about the linkset. For example, I might just want to  
express the general fact that A contains links to B, without saying  
anything about what predicate is used or what the subjects and objects  
are.

Hope that explains things.

Best,
Richard


> If people use two void:target
> statements as part of a linkset can we only assume that they are
> trying to include triples from both datasets at once? If so, the
> target's might contain anything resembling the statistics that one
> might be able to apply to directed linksets where one is really only
> trying to describe a subset of triples from void:subjectsTarget that
> happen to have object resources in another known dataset?
>
> Cheers,
>
> Peter
>
Received on Friday, 30 January 2009 15:05:00 UTC

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