Information I should have provided:
The error occurs at:
Caused by: java.lang.NullPointerException: null
at
org.apache.jena.n3.N3JenaWriterPP.preparePropertiesForSubject(N3JenaWriterPP.java:257)
at that line we find
if ( p.getURI().startsWith(RDF.getURI()) ||
since "p" is an anonymous node the getURI() returns null.
Claude
On Tue, Apr 28, 2015 at 10:47 PM, Claude Warren <[email protected]> wrote:
> I'm not sure this is an error so I thought I'd see what the consensus is
> here before I do anything.
>
> My understanding is that the Graph interface has no restrictions on the
> types of objects in the subject, predicate or object. That is that I could
> store an anonymous node as the predicate in a triple even though this is
> not allowed in a model.
>
> The FileGraph implementation uses a model internally and when it writes
> the data out the model restrictions seem to apply -- that is I can not
> store an anonymous node as a predicate.
>
> All other graphs tested thus far allow saving the anonymous node as a
> predicate.
>
> It may be that the format of the output is enforcing the restrictions. I
> am currently using a TURTLE format. However any functional format would be
> acceptable. Is there a way to write the filegraph output when the graph
> does not meet the model restrictions?
>
> Claude
>
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