1 research outputs found
Roget's Thesaurus as a Lexical Resource for Natural Language Processing
WordNet proved that it is possible to construct a large-scale electronic
lexical database on the principles of lexical semantics. It has been accepted
and used extensively by computational linguists ever since it was released.
Inspired by WordNet's success, we propose as an alternative a similar resource,
based on the 1987 Penguin edition of Roget's Thesaurus of English Words and
Phrases.
Peter Mark Roget published his first Thesaurus over 150 years ago. Countless
writers, orators and students of the English language have used it.
Computational linguists have employed Roget's for almost 50 years in Natural
Language Processing, however hesitated in accepting Roget's Thesaurus because a
proper machine tractable version was not available.
This dissertation presents an implementation of a machine-tractable version
of the 1987 Penguin edition of Roget's Thesaurus - the first implementation of
its kind to use an entire current edition. It explains the steps necessary for
taking a machine-readable file and transforming it into a tractable system.
This involves converting the lexical material into a format that can be more
easily exploited, identifying data structures and designing classes to
computerize the Thesaurus. Roget's organization is studied in detail and
contrasted with WordNet's.
We show two applications of the computerized Thesaurus: computing semantic
similarity between words and phrases, and building lexical chains in a text.
The experiments are performed using well-known benchmarks and the results are
compared to those of other systems that use Roget's, WordNet and statistical
techniques. Roget's has turned out to be an excellent resource for measuring
semantic similarity; lexical chains are easily built but more difficult to
evaluate. We also explain ways in which Roget's Thesaurus and WordNet can be
combined.Comment: Thesis submitted to the Faculty of Graduate and Postdoctoral Studies
in partial fulfillment of the requirements for the degree of Master of
Computer Science July, 2003. Ottawa-Carleton Institute for Computer Science,
School of Information Technology and Engineering, University of Ottawa,
Ottawa, Ontario, Canad