Indeed this helps, but it's still not clear weather and how I have to prepare the database for GeoSparlql queries.
I changed my query according to Greg's advice: PREFIX spatial: <http://jena.apache.org/spatial#> SELECT * WHERE { ?feature spatial:withinBox( 43.0 0.0 48.0 10.0 100 ) } LIMIT 100 but no results. Of course I checked that I have many triples with geo: coordinates within that rectangle : PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> SELECT * WHERE { ?S geo:lat ?LAT . ?S geo:long ?LON . } LIMIT 100 Regarding simple export from triples with geo: coordinates to GML or GeoJson, I'll write some code that I'll share. Jean-Marc Vanel <http://semantic-forms.cc:9112/display?displayuri=http://jmvanel.free.fr/jmv.rdf%23me> +33 (0)6 89 16 29 52 Le lun. 26 oct. 2020 à 16:38, Greg Albiston <[email protected]> a écrit : > Hi Jena-Marc, > > The namespace <http://geovocab.org/spatial#> is for NeoGeo Spatial > ontology, which has similarities to GeoSPARQL specification but is not > fully compliant. > > The Apache Jena spatial property functions use > <http://jena.apache.org/spatial#>. These are additional functions that > extend the GeoSPARQL standard. > > So you are likely getting no result as the "spatial:withinBox" function > in the query is undefined. > > Regarding your other question about GML and GeoJSON documents. The > GeoSPARQL standard doesn't cover serialisation from or to geospatial > document formats into the GeoSPARQL "Feature/Geometry/GeometryLiteral" > structure. This is likely because it is expected that most use cases > would stay in RDF format once setup. From my experience the GML > standards are also unbelievably convoluted to fully support. > > It may be straight forward to convert a list of points to a minimum GML > document that QGIS accepts. > > The "convert" functions are to harmonise a dataset to a single SRS and > datatype to reduce overhead and confusion from switching between > different formats when querying the data. Or to switch a dataset from > one SRS or datatype to another, i.e. consolidating diverse data sources. > They aren't for generating non-RDF spatial documents. These are also for > GeoSPARQL structure datasets so a dataset using the LatLon geo > predicates would need to be converted (for which the > "convertGeoPredicates" might be useful). > > Hope this helps, > > Greg > > > On 26/10/2020 14:17, Jean-Marc Vanel wrote: > > I missed ApacheCon, and I need some concrete hints sooner than next year. > > > > Currently my database gives an empty answer to : > > PREFIX spatial: <http://geovocab.org/spatial#> > > # ?feature spatial:withinBox(?latMin ?lonMin ?latMax ?lonMax [ ?limit]) > > SELECT * WHERE { > > ?feature spatial:withinBox( 43.0 0.0 46.0 10.0 100 ) > > } LIMIT 100 > > > > Should I apply once for all GeoSPARQLOperations.convert() ? > > static Dataset > > < > https://jena.apache.org/documentation/javadoc/arq/org/apache/jena/query/Dataset.html?is-external=true > > > > convert > > < > https://jena.apache.org/documentation/javadoc/geosparql/org/apache/jena/geosparql/configuration/GeoSPARQLOperations.html#convert-org.apache.jena.query.Dataset- > > > > (Dataset > > < > https://jena.apache.org/documentation/javadoc/arq/org/apache/jena/query/Dataset.html?is-external=true > > > > dataset) > > Convert the input dataset to the most frequent coordinate reference > system > > and default datatype. > > > > Jean-Marc Vanel > > < > http://semantic-forms.cc:9112/display?displayuri=http://jmvanel.free.fr/jmv.rdf%23me > > > > +33 > > (0)6 89 16 29 52 > > > > > > Le lun. 26 oct. 2020 à 11:02, Marco Neumann <[email protected]> a > > écrit : > > > >> good questions Jean-Marc, I will organize a session early in the new > year > >> to address some of them. In your case geo:lat and geo:long are not part > of > >> OGC GeoSPARQL but require a transformation. We have a tool in place for > >> that in Jena. And yes displaying large datasets need dedicated > strategies > >> for efficient processing. The points raised by you would make a good > >> problem statement for our session next year. Not sure if you have > attended > >> the ApachCon 2020 GeoSPARQL session last month but it's where I > >> mentioned further collaboration with third party tool developers as a > >> possibility. stay tuned. > >> > >> Marco > >> > >> > >> On Mon, Oct 26, 2020 at 9:14 AM Jean-Marc Vanel < > [email protected]> > >> wrote: > >> > >>> After reading the official > >>> https://jena.apache.org/documentation/geosparql/ > >>> I'm puzzled as to concrete how to . > >>> > >>> My simple export use case > >>> > >>> - I have a TDB 1 database with geo:lat and long properties; the > Jena > >>> geosparql dependency is added to my application > >>> - I have a LeafLet viewer able to display any RDF document with > >> geo:lat > >>> and long properties ; example map > >>> < > >>> > >> > https://semantic-forms.cc:1953/assets/geo-map/geo-map.html?link-prefix=http://semantic-forms.cc:1953/display?displayuri=&lang=fr&url=https://semantic-forms.cc:1953/sparql?query=%0APREFIX+form%3A+%3Chttp%3A%2F%2Fraw.githubusercontent.com%2Fjmvanel%2Fsemantic_forms%2Fmaster%2Fvocabulary%2Fforms.owl.ttl%23%3E+%0APREFIX+rdfs%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23%3E+%0APREFIX+geo%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2003%2F01%2Fgeo%2Fwgs84_pos%23%3E+%0APREFIX+foaf%3A+%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F%3E+%0A%0ACONSTRUCT+%7B%0A++%3Fthing+geo%3Along+%3FLONG+.%0A++%3Fthing+geo%3Alat+%3FLAT+.%0A++%3Fthing+rdfs%3Alabel+%3FLAB+.%0A++%3Fthing+foaf%3Adepiction+%3FIMG+.%0A%7D+WHERE+%7B%0A++graph+%3Fg+%7B%0A++++%3Fthing+%3Chttp%3A%2F%2Fpurl.org%2FNET%2Fc4dm%2Fevent.owl%23produced_in%3E+%3Chttp%3A%2F%2Fsemantic-forms.cc%3A1952%2Fldp%2FCormoz%3E+.%0A++%7D%0A++graph+%3Fgcoord+%7B%0A++++%3Fthing+geo%3Along+%3FLONG+.%0A++++%3Fthing+geo%3Alat+%3FLAT+.%0A++%7D%0A++OPTIONAL+%7B%0A+++graph+%3Fg1+%7B%0A++++%3Fthing+rdfs%3Alabel+%3FLAB+%7D+%7D%0A++OPTIONAL+%7B%0A+++graph+%3Fg2+%7B%0A++++%3Fthing+%3Curn%3AdisplayLabel%3E+%3FLAB+%7D+%7D%0A%0A++OPTIONAL+%7B%0A+++graph+%3Fg3+%7B%0A++++%3Fthing+foaf%3Adepiction+%3FIMG+%7D+%7D%0A++OPTIONAL+%7B%0A+++graph+%3Fg4+%7B%0A++++%3Fthing+foaf%3Aimg+%3FIMG+%7D+%7D%0A%0A++++OPTIONAL+%7B%0A+++graph+%3FgrCount+%7B%0A++++%3Fthing+form%3AlinksCount+%3FCOUNT.%0A++%7D+%7D%0A%7D%0AORDER+BY+DESC%28%3FCOUNT%29%0A > >>> ; but I found that JavaScript based displayers are falling on their > >>> knees > >>> (becoming very slow) for thousands of points > >>> - so I plan to use QGIS, so I need an export from RDF to one of the > >>> formats QGIS supports: GML, GeoJSON , etc > >>> > >>> How can I do that ? > >>> Do I have to use one of the convert* methods in > >>> > >>> > >> > https://jena.apache.org/documentation/javadoc/geosparql/index.html?org/apache/jena/geosparql/configuration/GeoSPARQLOperations.html > >>> ? > >>> > >>> Jean-Marc Vanel > >>> < > >>> > >> > http://semantic-forms.cc:1952/display?displayuri=http://jmvanel.free.fr/jmv.rdf%23me > >>> +33 (0)6 89 16 29 52 > >>> Twitter: @jmvanel , @jmvanel_fr ; chat: irc:// > irc.freenode.net#eulergui > >>> Chroniques jardin > >>> < > >>> > >> > http://semantic-forms.cc:1952/history?uri=http%3A%2F%2Fdbpedia.org%2Fresource%2FChronicle > >> > >> -- > >> > >> > >> --- > >> Marco Neumann > >> KONA > >> >
