Summary of workshop on lexicons for text extraction

The POETIC Lexicon Lynne Cahill, of the University of Sussex, England, presented the design an d specifications for the lexicon used in their Traffic Information Collator system, and what problem s they encountered in porting it to the MUC task . This is an information extraction system used by local police personnel for traffic reports . The domain is characterized by a fairly tight and limite d vocabulary, as well as a telegraphic style of syntax . Cahill discussed the relative ease with which th e lexicon was adapted to new police force domains . The general issues raised in Cahill's presentation were the problem of going from a sublanguag e lexicon to a broader lexicon, as required for the MUC-5 English Joint Venture domain . The portin g effort took 12 person months in 6 months time . The MUC-5 lexicon design consists of a domain specific lexicon and a phrasal lexicon . These were used in conjunction with the Alvey Natural Language Toolkit for parse recovery. Rich lexical information was added only to words which were significant in the domain as triggers for the template fills . Furthermore, the recognition of company and personal names was accomplished by standar d pattern matching techniques . Cahill discussed the different nature of the lexical entries in the two domains . Porting to MUC5 required a new semantics and much more syntax. The result was that the incomplete lexicon gave rise to undergeneration of appropriate template objects, while fragmentary parsing resulted in templat e overgeneration, because of the liberal acceptance of too many patterns . There was, furthermore, no contextual feedback into the parser, as well as no way of selecting the most likely analysis of a give n pattern, if several fired . Cahill pointed out that these problems were largely due to time constraint s in the development cycle, rather than the nature of the lexical design .