Stop using Nepomuk name and fix ontology URLs
The database schemas (ontologies) used in Tracker were created by a project called Nepomuk and they still carry that name.
The Nepomuk project has been dead for many years: its website 404s, all that's left is a Wikipedia article.
The idea of Nepomuk was interoperability between desktops by sharing a metadata vocabulary but this doesn't seem to have happened.
A key idea of RDF was that properties and classes are URLs which display their own documentation; but this relies on someone paying for a DNS record.
We could clear up some confusion by renaming the N* (nepomuk) ontologies to G* (gnome) and changing the URLs to point inside the gnome.org domain.