Support for Apache Jena Fuseki

Some time ago, mostly for lack of time, we stopped maintaining Knora’s support for the Apache Jena Fuseki triplestore. PR 1375 aims to reintroduce this support. So far, query performance with Fuseki is in some cases not as good as with GraphDB, but for now I’m only making a small attempt to optimise queries for Fuseki.

Just going through the conversations. I‘ll have look into it, when I‘m traveling. Very important job.
Regards, Erwin