% Animal classification, adapted from Eyelet's input/animal.pl.
%
% The Eyelet source uses Unicode predicate names; this eyepl version keeps the
% same tiny inheritance idea with plain vocabulary names.

% Output declarations: query/1 selects the relations written to this example's golden output.
query(type(X0, X1)).
query(subclassOf(X0, X1)).
query(succeeds(X0, X1)).

% Program structure: facts set up the scenario, and rules derive the queried conclusions.
human(joe).
animal(human).

% Derivation rules: each rule below contributes one logical step toward the displayed results.
animal(X) :- human(X).

type(joe, human) :- human(joe).
type(joe, animal) :- animal(joe).
subclassOf(human, animal) :- animal(human).
succeeds(animalExample, true) :- animal(_).