Firstly, there was exclude and NAF in iTQL:
> It was introduced to provide
> a limited form of negation, and one that interacts poorly with the
> open-world assumption. We also now have minus, which is well
> defined, corresponds closely to our intuitive understanding of the
> operation, and is (I am told) what was actually required.
> If my memory is correct we should probably at least deprecate, if
> not remove exclude entirely from mulgara.
> Do we agree that exclude should be removed?
Well *I* agree anyway. As you say, it doesn't do what anyone thinks
> If it should be removed, when should this occur?
And now adding the Jena API to Kowari cost customers:
Another possible reason is Tucana/Kowari/Mulgara’s Jena support - originally put in to provide a migration path for companies looking to move on from research projects to scalable infrastructure - which as Jena is the defacto semweb tool of choice, people used to evaluate Kowari’s scalability. Jena’s lack of scaling hurt us several times, I can remember lots of frantic calls as some company wrote us off because of our Jena API.
I'm current still working in this area (maybe somewhat surprisingly) and Jena still dominates (all of the tools I'm currently looking at are Jena based). And I still haven't seen a Jena implementation that scales (see page 10). Maybe the decision to open source Kowari cost another round of funding too. Maybe this is why Garlick or Radar Network's triple stores are still behind closed doors.