1. A system comprising: a processor; and a computer-readable storage device having instructions stored which, when executed by the processor, cause the processor to perform operations comprising: selecting a task-specific dialog motivator from a plurality of non-domain specific dialog motivators, wherein: the plurality of non-domain specific dialog motivators are not associated with any domain; each non-domain specific dialog motivator in the plurality of non-domain specific dialog motivators determines what action a dialog manager needs to take in conducting a dialog with a user using rules that act on instances of task knowledge; the plurality of non-domain specific dialog motivators comprise an assumption dialog motivator and a confirmation dialog motivator; and the task-specific dialog motivator is selected based on a comparison of user input to characteristics of each non-domain specific dialog motivator in the plurality of non-domain specific dialog motivators; and upon a spoken dialog system requesting further user input and invoking the confirmation dialog motivator to confirm the further user input: receiving the further user input; and when a confidence value associated with understanding the further user input is below a threshold value, invoking the assumption dialog motivator to present assumed further user input during a confirmation dialog.