Toward systems that understand spoken language

MIT´s Voyager system is an attempt to explore issues related to a fully interactive spoken-language system and natural language understanding. The system helps users get from one location to another within a specific geographical area, and can provide information about certain objects in the area. The current version of Voyager focuses on the city of Cambridge, Massachusetts, between MIT and Harvard University. Voyager´s domain knowledge (or backend) is an enhanced version of an existing direction assistance program (J.R. Davis and T.F. Trobaugh, 1987). The map database includes the locations of various classes of objects (streets, buildings, rivers) and their properties (address, phone number, etc.). To retrieve information, the Summit speech recognition system converts the user´s speech signal into a set of word hypotheses, the Tina natural language system interacts with Summit to obtain a word string and a linguistic interpretation of the utterance, and an interface between the two subsystems converts Tina´s semantic representation into the appropriate function calls to the back-end. Voyager then responds with a map, highlighting the objects of interest, plus an textual and spoken answer. The current implementation has a vocabulary of about 350 words and can deal with various types of queries, such as the location of objects, simple properties of objects, how to get from one place to another, and the distance and travel time between objects.<>