Awesome
GeoARQ
GeoARQ uses Lucene Spatial via an ARQ property function to allow to search nearby a location. All the RDF instances which use the WGS84 geo positioning RDF vocabulary [1] to represent geographic coordinates are indexed.
This is experimental (and unsupported).
How to use it
This is how you build an index from a Jena Model:
ModelIndexerSubject indexer = new ModelIndexerSubject("target/lucene");
indexer.indexStatements(model.listStatements());
indexer.close();
This is how you configure ARQ to use the spatial Lucene index:
IndexSearcher searcher = IndexSearcherFactory.create("target/lucene");
GeoARQ.setDefaultIndex(searcher);
This is an example of a SPARQL query using the :nearby property function to find airports close to Bristol (i.e. latitude ~ 51.3000, longitude ~ -2.71000):
PREFIX : <http://example/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX geoarq: <http://openjena.org/GeoARQ/property#>
PREFIX asc: <http://airports.dataincubator.org/schema/> .
SELECT ?label {
?s a asc:LargeAirport .
?s rdfs:label ?lavel .
?s geoarq:nearby (51.3000 -2.71000) .
}
Or, within a bounded box:
PREFIX : <http://example/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX geoarq: <http://openjena.org/GeoARQ/property#>
PREFIX asc: <http://airports.dataincubator.org/schema/> .
SELECT ?label {
?s a asc:LargeAirport .
?s rdfs:label ?lavel .
?s geoarq:within (51.3727 -2.72909 51.3927 -2.70909) .
}
Todo
- Add more tests
- Clean-up the code
- Add support for http://www.w3.org/2003/01/geo/wgs84_pos#lat_long
- Add ability to specify radius (i.e. geoarq:nearby (51.3000 -2.71000 20))
- Add ability to specify number of results within a radius (i.e. geoarq:nearby (51.3000 -2.71000 20 10))
- Investigate Geohash [2]
- Double check lucene-misc dependency, is it necessary?
- Add ability to index remote SPARQL endpoints?
- ...