Recursion is a technique in which one predicate uses itself $($maybe with some other predicates$)$ to find the truth value. We create a knowledge base in the file: recursion.pl$,$ inside this file we have two facts:

just$\_$ate$($deer$,$grass$).$ just$\_$ate$($tiger$,$ deer$).$

According to these facts we can get the conclusion that: is$\_$digesting$($deer$,$ grass$)$ is true and is digesting$($tiger$,$ deer$)$ is also true.

$//$ TODO: define the digesting relationship using recursive structures make the following

predicate to be true: is $\_$digesting$($tiger$,$grass$).$