I'm worried about our support for GeoSPARQL.
I personally never looked into this much before, but recently decided to do some digging, hoping to improve our documentation on RDF4J GeoSPARQL support.
As far as I can tell, our GeoSPARQL support is really minimal. The only geo function I managed to run is geof:distance, and even that failed when using it as part of a math _expression_ (e.g. dividing by 1000 to turn meters into kilometers). This is all the more worrying because that is the actual example query in our current documentation. I'm hoping that I have misunderstood something and we actually do support more than this, but I'd be grateful for some pointers.
I've put up a PR with a test case for this in rdf4j-testsuite, and tried to see about a fix in the LuceneSail, but to be fair I'm having a hard time figuring out the code. Is any of you available to invest a little time in understanding our GeoSPARQL support a little better and helping either fixing bugs or just improving the documentation?
At this point we need to either up our game in terms of documentation and support, or no longer claim we support this, because as it stands, claiming RDF4J "does GeoSPARQL" is false advertising, IMHO.
Regardless of anything else, our GeoSPARQL documentation is out of date because it still talks about spatial4j 0.4, and as not being included due to licensing problems, which is no longer the case (we include spatial4j 0.6). It also mentions JTS, but I have no idea how that relates to anything else (except that it seems to add polygon support but I don't understand how we would make that work). FWIW JTS itself is now also a LocationTech project so if we want, we can now add it as a dependency.
Jeen
