2 wheels, technically your talking about a DAO pull with second strike capability. It can be confusing at times since there are slight variances in how the triggers are defined and striker fired guns make it much more difficult.
I guess you can say that there are striker fired DAO guns and hammer fired DAO guns.
DAO striker: trigger pull does 2 actions, however the slide needs to be racked by hand or by firing in order to go to the next DAO pull.
DAO hammer: trigger does 2 actions, however another DAO pull can be accomplished weather the slide has been racked or not.
SAO striker or hammer: trigger pull does one action and needs the slide to be racked by hand or by firing in order to reset the striker or hammer to provide another SAO pull.