  The vocabulary of a continuous speech recognition (CSR) system is a
significant factor in determining its performance. In this paper, we present
three principled approaches to select the target vocabulary for a particular
domain by trading off between the target out-of-vocabulary (OOV) rate and
vocabulary size. We evaluate these approaches against an ad-hoc baseline
strategy. Results are presented in the form of OOV rate graphs plotted against
increasing vocabulary size for each technique.
