As far as I know, Siri doesn't have hard-coded voice commands, like 'SEND TEXT TO PAUL' articulated in a robotic voice. It aims to understands natural language with infinite variations.

One of the examples was: 'Do I need a raincoat today?' and you can continue 'How about tomorrow?' or 'where can I buy one?', and Siri understands the context. This is far far more advanced than any 'voice control' there is, and gives just a glimpse of what's coming.