In early 1997, our group initiated a project to develop jupiter, a conversational interface that allows users to obtain worldwide weather forecast information over the telephone using spoken dialogue. It has served as the primary research platform for our group on many issues related to human language technology, including telephonebased speech recognition, robust language understanding, language generation, dialogue modelling, and multilingual interfaces. Over a two year period since coming on line in May 1997, jupiter has received, via a toll-free number in North America, over 30,000 calls (totalling over 180,000 utterances), mostly from naive users. The purpose of this paper is to describe our development effort in terms of the underlying human language technologies as well as other system related issues such as utterance rejection and content harvesting. We will also present some evaluation results on the system and its components.

. We study determinization of weighted finite-state automata (WFAs), which has important applications in automatic speech recognition (ASR). We provide the first polynomial-time algorithm to test for the twins property, which determines if a WFA admits a deterministic equivalent. We also provide a rigorous analysis of a determinization algorithm of Mohri, with tight bounds for acyclic WFAs. Given that WFAs can expand exponentially when determinized, we explore why those used in ASR tend to shrink. The folklore explanation is that ASR WFAs have an acyclic, multi-partite structure. We show, however, that there exist such WFAs that always incur exponential expansion when determinized. We then introduce a class of WFAs, also with this structure, whose expansion depends on the weights: some weightings cause them to shrink, while others, including random weightings, cause them to expand exponentially. We provide experimental evidence that ASR WFAs exhibit this weight dependence. ...

The edit-distance of two strings is the minimal cost of a sequence of symbol insertions, deletions, or substitutions transforming one string into the other. The definition is used in various contexts to give a measure of the difference or similarity between two strings. This definition can be extended to measure the similarity between two sets of strings. In particular, when these sets are represented by automata, their edit-distance can be computed using the general algorithm of composition of weightes transducers comined with a single-source shortest-paths algorithm.