A directed dialogue prompt communicates a set of valid responses to the user (e.g. "How can I help you? ... Say something like, "account balance, order status," or "more options""). An open-ended prompt does not communicate a set of valid responses (e.g. "How can I help you?"). In both cases, the goal is to glean a valid spoken response from the user. The key difference is that with directed dialogue, the user is more likely to speak an option exactly as was communicated by the prompt (e.g. "account balance"). With an open-ended prompt, however, the user is likely to include extraneous words or phrases (e.g. "I was just looking at my bill and saw that my balance was wrong."). The open-ended prompt requires a greater degree of natural language processing to extract the relevant information from the phrase (i.e. "balance"). Open-ended recognition also requires a larger grammar set, which accounts for a wider array of permutations of a given response (e.g. "balance was wrong", "wrong balance", "balance is high", "high balance"). Despite the greater amount of data and processing required for open-ended prompts, they are more interactively efficient, as the prompts themselves are typically much shorter.