Trigger Behavior in Transactions

[Joshua Kramer <josh@xxxxxxxxxxxxxx>]

Greetings,

Where in the documentation can I find information on the low-level 
behavior of triggers that fire as a result of insert/update statements 
inside of transactions?

Do the triggers fire at the point the transaction is COMMITted?  Or as 
soon as the statements are encountered?  (If this is the case, how are 
rollbacks done - does the trigger also fire for the rollback?)

I am creating a mechanism for updating PG databases remotely (from another 
PG database) for a magazine article I'm writing, and I need to figure out 
how to engineer the trigger mechamisms so they work properly.

Thanks,
-Josh