% Source: http://www.cs.kuleuven.ac.be/~dtai/prototypes/dppd/advisor.html
what_to_do_today( _today, _weather, _program ):-
    kind_of_day( _today, _daykind ),
    kind_of_weather( _weather, _weatherkind ),
    proposal( _daykind, _weatherkind, _program ).

kind_of_day( monday, workday ). 
kind_of_day( thuesday, workday ).
kind_of_day( wednesday, workday ).
kind_of_day( thursday, workday ).
kind_of_day( friday, workday ).
kind_of_day( saturday, weekend ).
kind_of_day( sunday, weekend ).
kind_of_day( eastern, feastday ).
kind_of_day( first_of_may, feastday ).
kind_of_day( christmas, feastday ).
kind_of_day( new_years_day, badday ).
kind_of_day( friday_the_13th, badday ).

kind_of_weather( sunny, nice ).
kind_of_weather( rainy, nasty ).
kind_of_weather( foggy, nasty ).
kind_of_weather( windy, nasty ).

proposal( workday, _, go_to_work ).
proposal( weekend, nice, go_out_to_the_nature ).
proposal( weekend, nice, visit_the_golf_club ).
proposal( weekend, nice, wash_your_car ).
proposal( weekend, nasty, go_out_to_the_town ).
proposal( weekend, nasty, visit_the_bridge_club ).
proposal( weekend, nasty, enjoy_yourself_at_home ).
proposal( weekend, _, it_is_fun_to_learn_Japanese ).
proposal( badday, _, you_had_better_stay_in_bed ).
proposal( feastday, _weather, _program ) :-
    proposal( weekend, _weather, _program ).