Yet important practical considerations do arise when writing programs to understand one aspect or another of natural language utterances. Where, for example, a theorist w i l l characterize a parsing strategy according to its space and/or time requirements in attempting to analyze the worst possible input acc3rding to ~n a r b i t r a r y grammar s t r i c t l y limited in expressive power, the researcher studying Natural Language Processing can be j u s t i f i e d in concerning himself more with issues of practical performance in.
