In TheVerge: Siri's creators will unveil their new AI bot on Monday By Jacob Kastrenakes " .... Viv is essentially meant to be Siri, but good. It's an AI assistant that you speak to, but the difference here is that Viv is supposed to be able to handle complex requests and actually carry them out. The idea is that you could ask Viv to book you dinner and a movie, and it would just go ahead and do it. Siri, on the other hand, would make you ask those questions one at a time and then kick you over to OpenTable and Fandango to make your purchases. .... "
(UPdate) And more detail on Viv in Engadget.