Question about libeventdb

Hi
I'm writting a python application to sync GPE Calendar and Google Calendar.
Actually it works fine with single events.
 
Python has no module to use libeventdb.
So, I write and read directly in the GPE Calendar database.

Now I want to add the support of recurrent events.

I don't understand how the exceptions of recurrent events work.
I see it uses the "rexception" field in the "events" table.
But I don't understand more...

Can someone explain to me how this field works, or send me some good 
links ?

Thanks.

David.