negation (~α): strings not matched by α difference (α - β): strings matched by α but not β intersection (α & β): strings matched by α and β exclusive-or (

negation (~α): strings not matched by α difference (α - β): strings matched by α but not β intersection (α & β): strings matched by α and β exclusive-or (α ^ β): strings matched by α or β but not both inclusion (α > β): does α matches all strings β matches? equality (α = β): do α and β match exactly the same strings?