Bash Datalog: Answering Datalog Queries with Unix Shell Commands

I saw this paper just yesterday from another source. This is brilliant in it's simplicity and the performance is pretty impressive. I hope to write something like this in Julia.

Wondering if I'm missing something but the example is

fact(X, R, Y) :∼ cat facts.tsv

locatedIn(X, Y) :- fact(X, "locatedIn", Y).

locatedIn(X, Y) :- locatedIn(X, Z), fact(Z, "locatedIn", Y).

main(X) :- locatedIn(X, "USA")

I think line 3 could just be locatedIn(X, Y) :- locatedIn(X, Z), locatedIn(Z,Y).

unless I'm missing something.