ca'a/pu'i

[JORGE JOAQUIN LLAMBIAS <jorge@INTERMEDIA.COM.AR>]

Lojbab:
>>>[I don't know what the difference between ca`a and pu`i is.]
>>
>>Something to do with tenses, I suppose: {ca'a} contains an
>>implied {ca} and {pu'i} an implied {pu}.
 >
>The answer is that ca'a and pu'i are orthogonal to standard tense usage.
>They relate to potentiality of an event to occur, and not whether it
actually
>occurs.

Isn't {ca'a} = "actually occurs" and {pu'i} = "actually occurred"?
How can they not relate to whether the event actually occurs?

co'o mi'e xorxes