anchor.diff:  = GeoSPARQL
   
  -== SAILs, relation with Spatial4j / JTS and licenses
  +== SAILs, relation with Spatial4j / JTS
   
   Most of the geo heavy-lifting is performed by the SAILs, which also means that GeoSPARQL support (or lack thereof) depends on the SAIL being used.
  +Strictly speaking using a (text) search engine like Lucene is not required, but it will speed up spatial queries.
  +
  +=== Lucene
  +
  +By default, the Lucene SAIL only spatially indexes `http://www.opengis.net/ont/geosparql#asWKT` fields.
  +This can be changed using the `LuceneSail.WKT_FIELDS` parameter.
   
   The Lucene SAIL included in RDF4j uses a slightly outdated version of the https://www.locationtech.org/proposals/spatial4j[Spatial4j] library, 
   which in turn relies on an older version of the https://www.locationtech.org/projects/technology.jts[JTS] library for certain features.
  - 
  -This JTS library is not bundled with RDF4j due to license incompatibilities.
  +This JTS library is not bundled with RDF4j due to license issues.
   Future versions of RDF4j will likely solve this issue, as both Spatial4j and JTS are moving to https://www.locationtech.org[Eclipse LocationTech],
   and the JTS license will be changed.
   
   Meanwhile RDF4j users can use the Solr or ElasticSearch SAIL to connect to external search services.
  +
  +=== Providing your own SpatialSupportInitializer
  +
  +Another option is to implement a class `org.eclipse.rdf4j.query.algebra.evaluation.function.geosparql.SpatialSupportInitializer`.
  +For example, https://bitbucket.org/pulquero/sesame-geosparql-jts[Mark Hale's sesame-geosparql-jts].
   
   == WKT Literals
   
  
positive.code:                       res.getValue("dist").stringValue() + "km");   } );
  ----
  
  ===
  
  == Further reading
  
  
negative.code: 
  - http://www.opengeospatial.org/standards/geosparql[OGC GeoSPARQL specification]
  - https://en.wikipedia.org/wiki/Well-known_text[Wikipedia article on WKT]
  