datalog

A simple, unoptimized, purely functional Datalog implementation, inspired by miniKanren.

Includes naive, semi-naive, and backward-chaining implementations.

This implementation was originally created to accompany a presentation I gave about Datalog at the Clojure PDX meetup on March 1st, 2018. The slides from that presentation are in the doc directory here.

Feedback welcome!

References

Ceri, Stefano, Georg Gottlob, and Letizia Tanca. "What you always wanted to know about Datalog (and never dared to ask)." IEEE transactions on knowledge and data engineering 1.1 (1989): 146-166.

Ullman, Principles of Database and Knowledge-Base Systems Volume I, ch. 3

http://minikanren.org/

Syntax

Facts (atoms)

Entity-Attribute-Value (EAV) triples.

Example:

[Zeus :father Cronus]

Variables (lvars)

Symbols that start with a '?'.

Example:

?x

Rules

Vectors of atoms. The first element is the head of the rule and the rest are the body.

Example:

[[?x :grandparent ?y] [?x :parent ?z] [?z :parent ?y]]

"x has grandparent y, if x has parent z, and z has parent y."

Usage

See datalog_test.clj.

License

Copyright © 2018 Austin Haas

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.