Re: [dotNetRDF-Support] Rename a URI with dotNetRdf

[Rob V. <rv...@do...>]

Frank

Nodes are by design immutable objects

To change the subject/predicate/object of a triple you need to retract the
original triple and assert a replacement triple e.g.

INode newSubject = g.CreateUriNode(new Uri("http://new-uri.com"));
foreach (INode item in g.Triples.SubjectNodes.ToList())
{
  if (item.NodeType != NodeType.Uri) continue;
  List<Triple> ts = g.GetTriplesWithSubject(item).ToList();
  foreach (Triple t in ts)
  {
    g.Retract(t);
    g.Assert(newSubject, t.Predicate, t.Object);
  }
}

Note that it is necessary to use ToList() as otherwise you will get
concurrent modification exceptions

Alternatively you may be better off using a SPARQL Update if you are
ultimately transforming the stored data e.g.

DELETE
{
  <http://old-uri.com> ?p ?o .
}
INSERT
{
  <http://new-uri.com> ?p ?o .
}
WHERE
{
  <http://old-uri.com> ?p ?o .
}

Regards,

Rob

On 25/09/2014 14:52, "Frank Schumacher" <fs...@in...>
wrote:

>Hello,
>
>I want to write a programm that adds triples from a ttl-file to a
>virtuoso store. I load them with:
>
>IGraph g = new Graph();
>FileLoader.Load(g, @"filename");
>
>Before I add a triple, I want to check, wheter the element already
>exists in the virtuoso store (via
>http://www.w3.org/1999/02/22-rdf-syntax-ns#type and
>http://www.w3.org/2000/01/rdf-schema#label). If it exists, I want to
>replace the URI from the file with the URI from the virtuoso store.
>Unfortunately, I cannot rename an URI like
>
>foreach (INode item in g.Triples.SubjectNodes)
>   ((IUriNode)item).Uri = "newURI";
>
>Any idea how I can achieve this?
>
>Greetings,
>Frank
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