On 10/09/15 21:48, Mark Feblowitz wrote:
More on the subject -
After trying several options using Fuseki 1.3.0, I haven’t been able
to arrive at one Accept header setting that results in the
generation of JSON for both SELECT and CONSTRUCT queries.
In an accept header, you can ask for several formats.
"Accept: application/ld+json , application/sparql-result+json"
This is matched to the servers list of choices so the irrelevant one is
skipped.
Multiple "Accept" should also work but tools curl, wget seem to replace
multiple headers, not send both.
It is conceivable that I could send different commands for CONSTRUCT
(application/jd+json) versus SELECT (no header) but, as my system
supports both SELECT and CONSTRUCT, that’s a bit inconvenient.
An issue that may arise is what to do with the (JSON) results. A graph
is not a result set.
FYI, using the Fuseki web ui, the CONSTRUCT with Output: JSON
produces JSON-LD. Casting the same query as a SELECT, using Output:
JSON, produces the expected resultset in JSON.
Would you expect better outcomes using 2.3? If so, I’ll adapt my
configs to work with 2.3 and try it.
The default RDF format is Turtle not RDF/XML :-)
If what I’m seeing is the best outcome, I guess I’ll have to build
out as you suggest.
Andy
On Sep 10, 2015, at 3:42 PM, Mark Feblowitz
<[email protected]> wrote:
On Sep 10, 2015, at 2:20 PM, Andy Seaborne <[email protected]>
wrote:
On 10/09/15 19:06, Mark Feblowitz wrote:
I didn’t quite care that it was JSON-LD - only that I could get
json to be emitted. the application/rdf+json worked for this.
I’m using fuseki 1.0.1 at the moment.
There wasn't JSON-LD in Fuseki 1.0.0
Upgraded to Fuseki 1.3.0. Seems to require Java 8.
application/sparql-results+json returned RDF XML for me.
The Accept header application/ld+json worked, and provides an
option for post-query transformation.
When you say it worked for you, was that with CONSTRUCT or
SELECT?
CONSTRUCT and DESCRIBE
SELECT does not return graphs.
application/sparql-results+json returns JSON rsult sets.
Now I have a wish: As I’m viewing the results as output using
application/rdf+json, I am noticing that it’s very basic
triples. What the consumer of this result really wants is a
hybrid of triples and resultsets. So, it produces triples as
specified in the CONSTRUCT and it also incorporates variable
names into the JSON, as present in resultsets.
Talis's RDF/json format is intentionally simple.
That is, the emitted json is presented as URIs for the Subject,
Predicate, and Object (with additional syntax to handle
sub-parts and arrays of Objects). Tthe hybrid would somehow
also incorporate variable names, so instead of URI-S URI-P
URI-O it would be something like
{ S : {id : URI-S, [ { P: {id: URI-P, [ O: {id: URI-O} ] ] }}
] } }
where S, P, and O would be ?S, ?P, and ?O.
Doable? Something JSON-LD might be able to handle?
application/sparql-results+json ?
Otherwise you'll need to add an output format. Though easier
maybe 3-tier: use Fuseki as the database layer and have custom
formatter as a webservice running as a logic layer.
Or maybe Elda
http://www.epimorphics.com/web/tools/elda.html
Thanks
On Sep 10, 2015, at 1:39 PM, Andy Seaborne <[email protected]>
wrote:
On 10/09/15 18:20, Mark Feblowitz wrote:
Ok -
I tested all forms that you recommended, and the one that
does work is application/rdf+json.
Caveat - that's not JSON-LD.
https://jena.apache.org/documentation/io/rdf-json.html
Thanks very much for the suggestion!
Mark
On Sep 10, 2015, at 12:16 PM, Mark Feblowitz
<[email protected]> wrote:
That makes sense. But it doesn’t seem to work. I still
get it in RDF XML format.
I’m wondering whether the problem is with how I’m
submitting the query.
I’m using curl as follows:
curl -v -H "Content-Type:application/sparql-query" -H
“Accept: application/ld+json" -X POST
http://host:port/ds/sparql <http://host:port/ds/sparql>
-d …
Works for me (Fuseki1 and Fuseki2, latest).
Which version of Fuseki? (did it have JSON-LD?)
Andy
Should I instead be using a URL parameter?
Thanks,
Mark
On Sep 9, 2015, at 1:33 PM, Colin Maudry
<[email protected] <mailto:[email protected]>> wrote:
Hi Mark,
This is because CONSTRUCT doesn't return query results
(a table structure), but a graph.
Two possibilities :
* If you want to stick to your CONSTRUCT query and want
JSON out, you should request JSON-LD[1] with
"application/ld+json". You can also try
"application/json" or "application/rdf+json" to get
RDF/JSON (I never tried). According to the spec[2],
you're encouraged to use JSON-LD instead. * If you
really want JSON SPARQL results, that's a SELECT query
that you need to post.
I hope it helps.
Colin Maudry
[1] http://www.w3.org/TR/json-ld/
<http://www.w3.org/TR/json-ld/> [2]
http://www.w3.org/TR/rdf-json/
<http://www.w3.org/TR/rdf-json/>
On 09/09/2015 18:58, Mark Feblowitz wrote:
At my wits’ end here - when I invoke a SPARQL using
curl to a local Fuseki server, and the query is a
construct query, and I specify
-H “Accept: application/sparql-results+json”
or -H “Accept: application/sparql-results%2Bjson”
I consistently get results back in RDF/XML
<rdfs99:RDF xmlns:dp="http://dbpedia.org/property/
<http://dbpedia.org/property/>"
xmlns:yago="http://dbpedia.org/class/yago/
<http://dbpedia.org/class/yago/>"
xmlns:nsl="http://purl.org/ontology/storyline/“
<http://purl.org/ontology/storyline/%E2%80%9C> ...
With no "-H Accept…”, I’m seeing triples format.
In fact, no matter what I set the Accept header to, I
see rdf/xml. Without an Accept: header, I see
ntriples.
Any ideas?
