Datalog programs are values. You can store them in local variables, pass them as arguments, and return them. If you have two Datalog values you can combine them

Datalog programs are values. You can store them in local variables, pass them as arguments, and return them. If you have two Datalog values you can combine them into one (effectively it's just the union of them). This allows you to write small "Datalog fragments" and stitch them together into a larger program. The type system ensures that this stays meaningful. (I am one of the authors of Flix.)