% The Accounting Equation in Prolog %
% https://en.wikipedia.org/wiki/Accounting_equation %
% Created by Charles Hoffman, CPA (charles.hoffman@me.com). %
% Public domain: https://creativecommons.org/publicdomain/zero/1.0/ %
% Run SWI-Prolog using https://swish.swi-prolog.org/ %

term(asset).
term(liability).
term(equity).
structure(balanceSheet).
entity(microsoft).
period(2017).
assertion(does_balance_sheet_balance).

fact(term(asset), entity(microsoft), period(2017), 241086000000).
fact(term(liabilities), entity(microsoft), period(2017),168692000000).
fact(term(equity), entity(microsoft), period(2017),72394000000).

% rule Assets = Liabilities + Equity %
does_balance_sheet_balance(Entity, Period) :-
    fact(term(asset),entity(Entity),period(Period),Asset),
    fact(term(liabilities),entity(Entity),period(Period),Liabilities),
    fact(term(equity),entity(Entity),period(Period),Equity),
    Asset is Liabilities + Equity.

% QUESTION   fact(Term, Entity, Period, Value). %
% QUESTION   does_balance_sheet_balance(microsoft, 2017). %