EBL2: An Approach To Automatic Lexical Acquisition

A method for automatic lexical acquisition is out lined. An existing lexicon that, in addition Io ordinary ]exical entries, contains prototypical cntrips for various non-exclusive paradigms of open-cl~,.ss words, is extended by inferring new lexical entries from texts containing unknown words. This is done by comparing the constraints placed on the unknown words hy the natural language system's grammar with the prototypes and a number of hand-coded phras(, templates specific for each paradigm. Once a sufficient number of observations of the word in different contexts have been made, a lexical entry is constructed for the word by assigning it to one or sew~ral para-digm(s), Parsing sentences with ullknown words is normally very time-consuming due to the large nmn-ber of grammatically possible analyses. To cir~ cumvent this problem, other ilhrase templates are extracted automatically from tim gramlnal and domain-specific texts using an explanation based learning method. These templates represent grammatically correct, sentence patterns. When a sell-tence matches a template, the original I)arsing component can be bypassed, reducing parsing times dramatically .