9. A system comprising: a processor; and a computer-readable storage medium storing instructions which, when executed on a processor, cause the processor to perform operations comprising: generating a set of features characterizing an association between a user input and a conversation context using prior user inputs; determining, by normalizing a length of the user input to a previous input in the prior user inputs and using a data-driven machine learning approach, whether the user input is associated with an existing topic related to a previous conversation context; and when the user input is associated with the existing topic, generating a response to the user input using information associated with the user input and content associated with any previous user input on the existing topic.
9. A system comprising: a processor; and a computer-readable storage medium storing instructions which, when executed on a processor, cause the processor to perform operations comprising: generating a set of features characterizing an association between a user input and a conversation context using prior user inputs; determining, by normalizing a length of the user input to a previous input in the prior user inputs and using a data-driven machine learning approach, whether the user input is associated with an existing topic related to a previous conversation context; and when the user input is associated with the existing topic, generating a response to the user input using information associated with the user input and content associated with any previous user input on the existing topic. 15. The system of claim 9 , wherein generating the set of features further comprises using a semantic and syntactic analysis of the user input and the prior user inputs.