DB transaction support

Hi, I was just wondering a little about the transaction support in PEAR DB. Why is it designed to start the transaction at the first query after a call to autoCommit(false) and not something like begin()? In oracle for instance if I remember correctly you can have nested named transactions. With the pear approach you seem to be left with only one transaction that pear controls for you for all querys... I would have though a syntax like begin(transactionName) would have been a possibility but maybe I'm just lost somewhere in outer space. Please feel free to flame me or send me a spaceship. /Fredrik