Ungrammaticality and Extra-Grammaticality in Natural Language Understanding Systems

Among the components included in Natural Language Understanding (NLU) systems is a grammar which spec i f i es much o f the l i n g u i s t i c s t ruc tu re o f the ut terances tha t can be expected. However, i t is ce r ta in tha t inputs that are ill-formed with respect to the grammar will be received, both because people regularly form ungra=cmatical utterances and because there are a variety of forms that cannot be readily included in current grammatical models and are hence "extra-grammatical". These might be rejected, but as Wilks stresses, "...understanding requires, at the very least, ... some attempt to interpret, rather than merely reject, what seem to be ill-formed utterances." [WIL76]