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 >>>>>> >>>>>> >>>>>> >>>>> >>>> >>> >> >
