https://github.com/mumba-org/mumba
It's badly documented as i have just published to github, but i hope it gives a clue of how is supposed to work.
I'm on the final touches over this project, but the main concept is already working as is 90% of it, but i think exposing SQL is too raw, and maybe dont offer the whole picture, as for instance, what is important is not data, but sometimes pure computation.. Eg. suppose you offer a deep leaning inference where you receive and give back tensors..In the middle of it is a different sort of computation, where it doesnt have anything to do with databases.
Or yet, suppose you need to access something in a third-party before giving an answer, or if you want to do it in a distributed fashion without you api consumer even noticing it?
API's are a good answer to that, and in my opinion are superior interfaces, whatever the semantic web of the future will be, it will need this network of API peers to work as a floor to it.
For instance, you can design a Graph API on top of it. Exposing your data layer directly is bad engineering as there's a lot of problems you wont be able to solve, and where leaving clients to talk to "you" over a well-defined API will.
To put it simply, in my point of view the direction the semantic-web is pointing to is cool, but the answer is not the right one, and this idea of exposing SQLite directly while is cooler, yet have the same flaws, or else something as GraphQL would have taken the world as its not much a different answer than the one presented here.