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?
• ...

[1] http://www.w3.org/2003/01/geo/wgs84_pos#

[2] http://en.wikipedia.org/wiki/Geohash