user_query: check playoff tree on sports list
response_text: Which list?
user_query: check it off
response_text: Which list?
user_query: sports
response_text: OK, I added playoff tree.
user_query: add playoff tree to my list
response_text: OK. Which list do you want to add to?
User: Call Mary on Alexa.
Parse: Initiate_call ( callee Personal_contact ( person « Mary » ) provider « Alexa » )