PPT Slide
weather( sunday , fair ).
weather( monday , overcast ) .
weather( tuesday , fair ) .
weather( wednesday , fair ) .
weather( thursday , overcast ) .
weather( friday , rainy ) .
weather( saturday , overcast ) .
active( birds , sunday ) .
active( birds , tuesday ) .
active( birds , thursday ) .
observed( rarebird , wednesday ) .
observed( rarebird , friday ) .
happy( birders , Day ) : - weather( Day , fair ) ,
happy( birders , Day ) : - observed( rarebird , Day ) .
|? - happy( birders , When ) .