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Re: json-ld and sparql

From: John Walker <john.walker@semaku.com>
Date: Tue, 15 Mar 2016 19:01:37 +0000
To: Kingsley Idehen <kidehen@openlinksw.com>
CC: "public-linked-json@w3.org" <public-linked-json@w3.org>
Message-ID: <28CC5A16-B5D6-4DDB-9CB7-FF4F649ABCBB@semaku.com>
Hi Kingsley,

On 15 Mar 2016, at 17:21, "Kingsley Idehen" <kidehen@openlinksw.com<mailto:kidehen@openlinksw.com>> wrote:

On 3/15/16 11:53 AM, John Walker wrote:
Hi Jean-Claude,

Try using the CONSTRUCT form of SPARQL and use Accept header to request results in JSON-LD.

prefix schema: <<http://schema.org/>http://schema.org/>
construct where {
?p a schema:Place .
?p rdfs:label ?name .
?p geo:lat ?lat .
?p geo:long ?lon .


Hi John,

As per my earlier comment, the following will do:

prefix schema: <<http://schema.org/>http://schema.org/>
describe ?p where {
?p a schema:Place .
?p rdfs:label ?name .
?p geo:lat ?lat .
?p geo:long ?lon .

Sure, but you may also get a bunch of extra data you don't want/need.

Main point is to use a query that returns a graph response rather than a table.

and the JSON-LD set as the output format.

SPARQL Query Editor Source Code Link:

curl -i "http://dbpedia.org/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&qtxt=prefix+schema%3A+%3Chttp%3A%2F%2Fschema.org%2F%3E%0D%0Adescribe++%3Fp++where+%7B%0D%0A%3Fp+a+schema%3APlace+.%0D%0A%3Fp+rdfs%3Alabel+%3Fname+.%0D%0A%3Fp+geo%3Alat+%3Flat+.%0D%0A%3Fp+geo%3Along+%3Flon+.%0D%0A%7D+LIMIT+5&format=application%2Fld%2Bjson&CXML_redir_for_subjs=121&CXML_redir_for_hrefs=&timeout=30000&debug=on"<http://dbpedia.org/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&query=prefix+schema%3A+%3Chttp%3A%2F%2Fschema.org%2F%3E%0D%0Adescribe++%3Fp++where+%7B%0D%0A%3Fp+a+schema%3APlace+.%0D%0A%3Fp+rdfs%3Alabel+%3Fname+.%0D%0A%3Fp+geo%3Alat+%3Flat+.%0D%0A%3Fp+geo%3Along+%3Flon+.%0D%0A%7D+LIMIT+5&format=application%2Fld%2Bjson&CXML_redir_for_subjs=121&CXML_redir_for_hrefs=&timeout=30000&debug=on>


On 15 Mar 2016, at 14:35, "Jean-Claude Moissinac" <<mailto:jean-claude.moissinac@telecom-paristech.fr>jean-claude.moissinac@telecom-paristech.fr<mailto:jean-claude.moissinac@telecom-paristech.fr>> wrote:

I'm trying to find best practices in the use of a json output from a sparql endpoint
For exemple the request on dbpedia :
prefix schema: <<http://schema.org/>http://schema.org/>
select distinct ?p ?name ?lat ?lon where {
?p a schema:Place .
?p rdfs:label ?name .
?p geo:lat ?lat .
?p geo:long ?lon .
give me as json output

{ "head": { "link": [], "vars": ["p", "name", "lat", "lon"] },
  "results": { "distinct": false, "ordered": true, "bindings": [
    { "p": { "type": "uri", "value": "http://dbpedia.org/resource/Cameron_Parish,_Louisiana" }  , "name": { "type": "literal", "xml:lang": "en", "value": "Cameron Parish, Louisiana" } , "lat": { "type": "typed-literal", "datatype": "http://www.w3.org/2001/XMLSchema#float", "value": "29.85" }    , "lon": { "type": "typed-literal", "datatype": "http://www.w3.org/2001/XMLSchema#float", "value": "-93.2" }},
    { "p": { "type": "uri", "value": "http://dbpedia.org/resource/Cameron_Parish,_Louisiana" }  , "name": { "type": "literal", "xml:lang": "ar", "value": "\u0645\u0642\u0627\u0637\u0639\u0629 \u0643\u0627\u0645\u064A\u0631\u0648\u0646 (\u0644\u0648\u064A\u0632\u064A\u0627\u0646\u0627)" }        , "lat": { "type": "typed-literal", "datatype": "http://www.w3.org/2001/XMLSchema#float", "value": "29.85" }    , "lon": { "type": "typed-literal", "datatype": "http://www.w3.org/2001/XMLSchema#float", "value": "-93.2" }},
... < cut for clarity >

 }} ] } }

We loose the fact that ?p is a Place. We can factorize the 'type' on the table of results. And finally get a table of objects like thos one
    "p ":  "http://dbpedia.org/resource/Cameron_Parish,_Louisiana",
"name": "Cameron Parish, Louisiana",
"pos": { "lat": 29.85, "long": 93.2 }
I suppose some results can be obtained by using a context and some others by framing.
Can we point me on ideas for clarification?
Many thanks in advance
Jean-Claude Moissinac

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Kingsley Idehen
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Received on Tuesday, 15 March 2016 19:02:16 UTC

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