We noted at the beginning of the chapter that, although the question ``Can you tell me how to get to the gallery in the square containing the monument?'' taken literally, appears to be asking a yes-no question, it is in fact an indirect request for information. An important area of natural language processing in recent years has been that of understanding and generating so-called speech acts. The notion goes back to the Oxford philosopher J. L. Austin, who in a book entitled How to Do Things with Words (1962), noted that some sentences seem not simply to make statements, but, in their utterance, to perform the acts that they mention. When I say ``I promise to fix your car for you'' or ``I bet you twenty pounds that it rains this afternoon,'' I am not simply saying that I promise or that I bet: I am actually making that promise or bet by uttering the sentence. This idea was generalized to cover all sentences by a student of Austin's, John Searle, in a book entitled Speech Acts (1969). For example, in saying ``There's a fly in your soup,'' I am not simply uttering words; I am, subject to certain conditions being fulfilled, performing the act of making an assertion. (Searle calls these the `preparatory', `sincerity', and `essential' conditions. We shall not discuss them here; you can find out more about the nature of speech acts by looking at Searle's book.) Likewise, in uttering ``What's the time?'' I am performing the act of making a request. Sometimes, however, the syntactic form of a sentence is not a good guide to the act it is performing. For example, ``There's a fly in your soup'' may not be a simple assertion but, in context, a warning not to drink it. Likewise, the question ``What's the time?'' might, in a situation in which you are looking for an excuse to get rid of an unwelcome guest, be intended as a suggestion that the guest leave. The use of direct and indirect speech acts in conversation has been well studied by a number of linguists, cognitive scientists, and philosophers, including Grice (1975), Cohen and Perrault (1979), and Allen and Perrault (1980).