Hi Stian,
Many thanks for the explanation
Best,
Andrea
On 14 May 2015 21:35, "Stian Soiland-Reyes" <[email protected]> wrote:
> BTW, for arbitrary "dummy" or example graphs it might be better to name
> them using example.com and friends (.org, .net) which are exactly for that
> purpose. E.g.
>
> SELECT ?s WHERE {
> GRAPH <http://example.com/graph1> {
> ?s ?p ?o .
> }
>
> That way it is more obvious to future readers of your code (e.g. your
> future self!) that you deliberately did not mean the actual location on the
> web.
>
> In production, for similar arbitrary graphs which do not have a
> corresponding web namespace, you can generate graph names like urn:uuid:
> b213bf89-92be-42b9-9a6c-2566519c710c (see java.util.UUID) - which admitedly
> are less fun for debugging, but unique, at least in the current solar
> system.
>
> These also have the "advantage" of not working at all with FROM.
> On 13 May 2015 21:51, "Andrea Gazzarini" <[email protected]> wrote:
>
> > Ok I got you, many thanks.
> > I thought I could create a named graph with an arbitrary URI, put some
> data
> > and then use that URI in the FROM keyword.
> >
> > Thanks again
> > Andrea
> > On 13 May 2015 22:36, "Andy Seaborne" <[email protected]> wrote:
> >
> > > On 13/05/15 20:16, Andrea Gazzarini wrote:
> > >
> > >> Hi Andy,
> > >> Thank you very much for the explanation. But I still miss the point:
> as
> > >> you
> > >> said, the FROM keyword set / fills the default graph so assuming I
> > >> previously loaded a triple under http://graph1.com
> > >>
> > >> Running
> > >>
> > >> SELECT ?s FROM <http://graph1.com> { ?s ?p ?o }
> > >>
> > >> I should get the subject of that triple. Is that correct? Because the
> > code
> > >> above is running under this exact scenario and I'm getting no result.
> > >>
> > >
> > > It will do an HTTP GET on http://graph1.com -- it does not get it from
> > > the dataset because its the dataset to be queried that is being
> > described.
> > >
> > > (graph1.com happens to exist and it returns junk.)
> > >
> > > Andy
> > >
> > >
> > >> Kind Regards,
> > >> Andrea
> > >> On 13 May 2015 21:05, "Andy Seaborne" <[email protected]> wrote:
> > >>
> > >> 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" <[email protected]>
> 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 <
> [email protected]>
> > >>>>> 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
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>
> > >>>>
> > >>>
> > >>
> > >
> >
>
