[cjo]

I'm not sure how high the adoption rate is but it's a natural extension of immutable data into the database world.

It also has some old roots in the Lisp community, lectures 8A and 8B[0] of MIT's famous SICP course and section 4.4 of the book[1] are on creating a logic programming language similar to Prolog; and Datomic's query language is Datalog which is a subset of Prolog.

[0] - http://ocw.mit.edu/courses/electrical-engineering-and-comput... [1] - http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-29.html...