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Re: RDF-ISSUE-82 (TriG repeated graph iris): How should repeated graph iri labels be handled in TriG [RDF Turtle]

From: Gavin Carothers <gavin@carothers.name>
Date: Wed, 21 Dec 2011 10:01:58 -0800
Message-ID: <CAPqY83yaxpf+hLWA_f2F12NSZMzXzV77VL295hMxx3grA6obiw@mail.gmail.com>
To: RDF Working Group WG <public-rdf-wg@w3.org>
On Wed, Dec 21, 2011 at 9:53 AM, RDF Working Group Issue Tracker
<sysbot+tracker@w3.org> wrote:
>
> RDF-ISSUE-82 (TriG repeated graph iris): How should repeated graph iri labels be handled in TriG [RDF Turtle]
>
> http://www.w3.org/2011/rdf-wg/track/issues/82
>
> Raised by: Gavin Carothers
> On product: RDF Turtle
>
> There are a number of ways of handling the case of multiple instances of a graph iri labelling a number graph statements.
>
> Sample TriG Document:
>
> @base <http://example.com/>
> <graph> { <s> <p> <o> . }
> <graph> { <s2> <p> <o2> . }
>
> 1) Disallowed (TriG input document behaviour)
>
> "In a TriG document a graph IRI must not be used to label more then one graph."
>
> Result: Parse Error

This is my personal preference, and what the original TriG input
document said. A merge based syntax would be N-Quads which -has- to be
merge based. But this is not a strongly held opinion.

>
> 2) Merge
>
> "In a TriG document graph statements with the same graph IRI should be merged to form a single RDF Graph."
>
> Result:
> @base <http://example.com/>
> <graph> { <s> <p> <o> .
>          <s2> <p> <o2> . }
>
> Note: BlankNode labels in each graph statement would either result in shared blank nodes or independent blank nodes (??)

Some implementations do this already.

>
> 3) Replace
>
> "Upon encountering a graph statement with the same graph IRI of another graph statement, the most recently parsed RDF Graph should replace the earlier one in the RDF Dataset."
>
> Result:
> @base <http://example.com/>
> <graph> { <s2> <p> <o2> . }

I am unaware of any implementations that do replacement this way with TriG.

>
> 4) Ignore
>
> "Graph statements with a repeated graph IRI are ignored. Only the first graph statement is added to the RDF Dataset."
>
> Result:
> @base <http://example.com/>
> <graph> { <s> <p> <o> . }

While some implementations have done this from time to time, I'm
reasonably sure this was a BUG.

>
> 5) Document Decides
>
> Apply one of 1-4 on the basis of a directive "@policy". Default to Disallowed.

Not really thrilled with the idea. But would allow Disallow and Merge
to co-exist. Default could go either way.

>
>
>
>
>
Received on Wednesday, 21 December 2011 18:02:26 GMT

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