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11 - LKB Encoding of Lexical Knowledge
- Edited by Ted Briscoe, Ann Copestake, Valeria de Paiva
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- Book:
- Inheritance, Defaults and the Lexicon
- Published online:
- 01 April 2010
- Print publication:
- 28 January 1994, pp 190-222
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- Chapter
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Summary
Introduction In setting up a lexical component for natural language processing systems, one finds that a considerable amount of information is often repeated across sets of word entries. To make the task of grammar writing more efficient, shared information can be expressed in the form of partially specified templates and distributed to relevant entries by inheritance. Shared information across sets of partially specified templates can be factored out and conveyed using the same technique. This makes it possible to avoid redefining the same information structures, thus reducing a great deal of redundancy in the specification of word forms. For example, general properties of intransitive verbs concerning subcategorization and argument structure can be simply stated once, and then inherited by lexical entries which provide word specific information, e.g. orthography, predicate sense, aktionsart, selectional restrictions. Likewise, properties which are common to all verbs (e.g. part of speech, presence of a subject) or subsets of the verb class (presence of a direct object for transitive and ditransitive verbs) can be defined as templates which subsume all members of the verb class or some subset of it. This approach to word specification provides a highly structured organization of the lexicon according to which the properties of related word types as well as the relation between word types and specific word forms are expressed in terms of structure sharing and inheritance (Flickinger, Pollard and Wasow, 1985; Flickinger, 1987; Pollard and Sag, 1987, pp. 191–209).
9 - The ACQUILEX LKB: An Introduction
- Edited by Ted Briscoe, Ann Copestake, Valeria de Paiva
-
- Book:
- Inheritance, Defaults and the Lexicon
- Published online:
- 01 April 2010
- Print publication:
- 28 January 1994, pp 148-163
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- Chapter
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Summary
Introduction
This chapter and those following describe the LKB, a lexical knowledge base system which has been designed as part of the ACQUILEX project to allow the representation of syntactic and semantic information semi-automatically extracted from machine readable dictionaries (MRDs) on a large scale. An overview of the ACQUILEX project is given by Briscoe (1991).
Although there has been previous work on building lexicons for Natural Language Processing (NLP) systems from MRDs (e.g. Carroll and Grover, 1989), most attempts at extracting semantic information have not made use of a formally defined representation language; typically a semantic network or a frame representation has been suggested, but the interpretation and functionality of the links has been left vague. Several networks based on taxonomies extracted from MRDs have been built (following Amsler, 1980) and these are useful for tasks such as sense-disambiguation, but are not directly utilisable as NLP lexicons. For a lexicon to be genuinely (re)usable, a declarative, formally specified, representation language is essential. A large lexicon has to be highly structured; it is necessary to be able to group lexical entries and to represent relationships between them, both in order to capture linguistic generalisations and to achieve consistency and conciseness. But, unless these notions of structure are properly specified, a lexicon based on them is in danger of being incomprehensible except (perhaps) to its creators.
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