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https://issues.apache.org/jira/browse/JENA-1069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15006698#comment-15006698
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Andy Seaborne commented on JENA-1069:
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Re: [comment on
JENA-1064|https://issues.apache.org/jira/browse/JENA-1064?focusedCommentId=15006586&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15006586]
{{Quad.tripleInQuad}} is just a marker for a triple being put in a quad for
transport around. It should be used rarely and temporarily. It's more of a
"don't know", or "don't care"marker i.e. nothing meaningful can go there. It is
not referencable in SPARQL for example. I'll track down it's uses which I hope
are few and far between. It has got confused with
{{Quad.defaultGraphNodeGenerated}} in the parsers.
> Simpify the internal naming of the default graph (Quad constants)
> -----------------------------------------------------------------
>
> Key: JENA-1069
> URL: https://issues.apache.org/jira/browse/JENA-1069
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 3.0.0
> Reporter: Andy Seaborne
> Assignee: Andy Seaborne
>
> There are two different constants for the default graph for what seemed at
> the time, slightly different situations. The idea was that quads from the
> default graph of a dataset would be {{Quad.defaultGraphIRI}} and quads
> created by parsers, would be {{Quad.defaultGraphNodeGenerated}}. The idea was
> that the output of the parser was "default graph" but it was being redirected
> into a named graph. This does not now seem useful.
> {{Quad.defaultGraphIRI}} = {{<urn:x-arq:DefaultGraph>}}
> {{Quad.defaultGraphNodeGenerated}} = {{<urn:x-arq:DefaultGraphNode>}}
> In SPARQL, the application is using {{GRAPH <urn:x-arq:DefaultGraph>}}. Using
> {{<urn:x-arq:DefaultGraphNode>}} wil not work consistently.
> The proposal is to combine these two as {{Quad.defaultGraphIRI}}, possible
> migrate to {{Quad.defaultGraph}}, or even a class or enum for the graph
> naming constants.
> These constants should never have been written to disk in database, certainly
> not {{<urn:x-arq:DefaultGraphNode>}}, but just to make sure, the operation
> {{Quad.isDefaultGraph(Node)}} can take the old name into account for a
> release cycle.
> Nearly all the changes are in tests where the expected output has been
> explicitly written into test results.
> There is another, little used, constant -- {{Quad.tripleInQuad}} -- for when
> a triple is in a quad just to be transported around, meaning "meaningless",
> "unknown" or "doesn't matter". This would not change. It exists to be
> different from {{Quad.defaultGraphIRI}}.
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