13. A method comprising: receiving a first audio signal representing first user speech; identifying, using the first audio signal, a first activity and a second activity associated with a first domain; identifying, using the first audio signal, a third activity associated with a second domain; sending a second audio signal representing a first question associated with the first domain and the second domain; receiving a third audio signal representing second user speech; selecting the first domain based at least in part on the third audio signal; determining, based at least in part on the first activity and the second activity, to request at least one additional piece of information; based at least in part on determining to request the at least one additional piece of information, sending a fourth audio signal representing a second question for the at least one additional piece of information; receiving a fifth audio signal representing third user speech; and selecting the first activity based at least in part on the fifth audio signal.
13. A method comprising: receiving a first audio signal representing first user speech; identifying, using the first audio signal, a first activity and a second activity associated with a first domain; identifying, using the first audio signal, a third activity associated with a second domain; sending a second audio signal representing a first question associated with the first domain and the second domain; receiving a third audio signal representing second user speech; selecting the first domain based at least in part on the third audio signal; determining, based at least in part on the first activity and the second activity, to request at least one additional piece of information; based at least in part on determining to request the at least one additional piece of information, sending a fourth audio signal representing a second question for the at least one additional piece of information; receiving a fifth audio signal representing third user speech; and selecting the first activity based at least in part on the fifth audio signal. 14. A method as recited in claim 13 , further comprising: determining, based at least in part on the first domain, that the first activity cannot be performed without sending the second audio signal.