Towards Understanding Spontaneous Speech: Word Accuracy vs. Concept   Accuracy
  In this paper we describe an approach to automatic evaluation of both the speech recognition and understanding capabilities of a spoken dialogue system for train time table information. We use word accuracy for recognition and concept accuracy for understanding performance judgement. Both measures are calculated by comparing these modules' output with a correct reference answer. We report evaluation results for a spontaneous speech corpus with about 10000 utterances. We observed a nearly linear relationship between word accuracy and concept accuracy. 
M. Boros, W. Eckert, F. Gallwitz, G. Goerz, G. Hanrieder, H. Niemann   (Bavarian Research Center for Knowledge-Based Systems...