A Sign Expansion Approach to Dynamic, Multi-Purpose Lexicons

A Sign Expansion Approach to Dynamic, Multi-Purpose Lexicons Jon Atle Gulla GMD - IPSI Dolivostratle 15 D-64293 Darmstadt, Germany gulla0gmd, de. Sjur NCrsteb¢ Moshagen Computing Centre for the Humanities Harald H£rfagres gt. 31, N-5007 Bergen, Norway s jut. mo shagen0hd, uib. no Abstract Two problematic issues in most lexi- con systems today are their size and re- stricted domain of use. In this paper, we introduce a new approach to lexical or- ganization that leads to more compact and flexible lexicons. The lexical en- tries are conceptual/phonological frames rather than word entries, and a num- ber of expansion rules are used to gen- erate entries of actual words from these frames. A single frame supports not only all forms of a word, but also words of dif- ferent categories that are derived from the same semantic basis. The whole theory is now being implemented in the TROLL lexicon project. 1 Introduction Due to the complexity and wide coverage of lex- ical information, full-fledged lexicon systems eas- ily grow undesirably big and must cope with in- tricate ~ nets of dependencies among lexical items. For keeping the speed of access at a satisfactory level, lexical information is often repeated in dif- ferent entries to reduce the number of consulta- tions needed for a single user query. This sim- plifies and speeds up the access of lexical infor- mation, but also blows up the size of the lexi- con and leads to huge maintenance problems. In many cases, it also clutters the lexicon structure, so that important lexical relationships and gener- alizations are lost. Structuring the lexicon in inheritance hierar- chies opens for more compact lexicon represen- tations. So far, lexicons have been structured in syntactic inheritance hierarchies, in which more or less abstract syntactic classes form the upper nodes and actual words are associated with the leaf nodes (Flickinger and Nerbonne, 1992; Rus- sell et al., 1992). However, the nature and num- ber of these abstract syntactic classes are not very clear, and it seems difficult to come up with a sound method for how to decide on such classes. At the same time, there are also good reasons for assuming a similar hierarchy based on seman- tic properties (Hellan and Dimitrova-Vulchanova, 1994). Representing many competing hierarchies in the lexicon is a problem in itself and is here even more problematic as there are many com- plex relationships between semantic and syntac- tic properties (Gropen et al., 1992; Hellan and Dimitrova-Vulchanova, 1996). Another problem is related to the notions and structures adopted in the lexicon systems. Most lexicons today are constructed within the frame- work of some syntactic theory. This theory guides the structuring of lexical information and also de- cides what information should be available to the user (Andry et al., 1992; Flickinger and Nerbonne, 1992; Mel'Suk and Polgu~re, 1987; Russell et ~l., 1992; Krieger and Nerbonne, 1991). Some lexicon systems try to be reasonably theory-independent, though they still have to adopt some basic syn- tactic notions that locate them …

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