Construction of language models for spoken database queries

In this paper we describe the construction of language models (finite-state networks) for a question-answering system handling database queries via spoken input(German), and report on sentence-understanding experiments with them. The world model representing the content of the permitted questions is given by a semantic structure with 5 object classes, 3 additional attribute classes and 14 relations between them The sentence structures (6 main types) are organized as a regular grammar. Acoustic recognition experiments show that the perplexity rather than the number of transitions determines the search expenditure and the error rate.