I am reading Natural Language Understanding by James Allen.
It has the following sentence
That John is rich implies that he is happy.
And first-order logic representation as
RICH(JOHN1) $\supset$ HAPPY(JOHN1)
I think it is incorrect and should be written as
RICH(JOHN1) $\subset$ HAPPY(JOHN1)
since rich only subset, there are probably other things that make John happy.
I am quite confident that it is not a typo, but why it is written this way.