Re: Help on FROM keyword

[Andy Seaborne]

FROM describes the dataset to use.

GRAPH accesses the data.
FROM <http://example/data> set the default graph from the contents of 
http://example/data by reading that URL. (This is for the general 
purpose dataset - TDB is slightly different but the principle is the same)

        Andy

On 13/05/15 18:57, Andrea Gazzarini wrote:
Hi Trevor,
Thanks, yes that works...but I would like to understand what is wrong with
my example

Thanks again
Andrea
On 13 May 2015 19:54, "Trevor Donaldson" <tmdona...@gmail.com> wrote:

Hi Andrea,

Can I suggest trying this ..

SELECT ?s
WHERE {
   GRAPH <http://graph1.com> {
   ?s ?p ?o
  }
}

On Wed, May 13, 2015 at 1:26 PM, Andrea Gazzarini <gxs...@gmail.com>
wrote:

Hi,
A question about the FROM keyword. I have the following data

<http://graph1.com> = { <http://a.b.c/s1> <http://a.b.c/p1> <
http://a.b.c/o1>
. }
<http://graph2.com> = { <http://a.b.c/s2> <http://a.b.c/p2> <
http://a.b.c/o2>
. }

For simplicity, I created a file for each triple (file1.nt and file2.nt).
Then, I loaded those data using the following code:

Dataset memoryDataset = DatasetFactory.createMem();
Model memoryModel = ModelFactory.createDefaultModel();
memoryModel.read(new FileReader("file1.nt"), "http://e.org";,
"N-TRIPLE");
memoryDataset.addNamedModel("http://graph1.com";, memoryModel);

memoryModel = ModelFactory.createDefaultModel();
memoryModel.read(new FileReader("file2.nt"), "http://e.org";,
"N-TRIPLE");
memoryDataset.addNamedModel("http://graph2.com";, memoryModel);

I'm not understanding the results coming from the following query:

SELECT ?s FROM <http://graph1.com> { ?s ?p ?o }

?s = <nothing>

I was expecting

?s=<http://a.b.c/s1>

Am I missing something? I'm using Jena 2.12.1

Thanks in advance for your help
Andrea