Onto.PT: Towards the Automatic Construction of a Lexical Ontology ...

42 Chapter 3. Related Work
• part, n: a piece of something;
• piece, n: a portion of some material;
Amsler (1981) believes that these loops are usually the evidence of a truly primitive
concept, such as the set containing the words class, group, type, kind, set,
division, category, species, individual, grouping, part and section. These primitives
are often related with “covert categories” (Ide and Véronis, 1995), which are concepts
that do not correspond to any particular word and are introduced to represent
a specific category or group of concepts. For instance, there is no word to describe
the hypernym of the concepts described by tool, utensil, implement and instrument,
so a new “covert” hypernym, instrumental-object, is artificially created.
Chodorow et al. (1985) introduced the notion of “empty heads”. Words belonging
to this small class (e.g. one, any, kind, class, manner, family, race, group,
complex) might occur in the beginning of the definition followed by the preposition
of, but do not represent the superordinate concept. Guthrie et al. (1990) explored
the class of “empty heads” to extract other semantic relations, besides hyponymy.
For instance, the word member is related with the member-set relation (Markowitz
et al., 1986) and the word part is related with the is-part relation (included by Amsler
(1981) in his tangled hierarchies). Concerning this problem, Nakamura and Nagao
(1988) provide a list of function nouns that appear in the beginning of dictionary
definitions, and the relations they are usually associated with:
• kind, type → is-a
• part, side, top → part-of
• set, member, group, class, family → membership
• act, way, action → action
• state, condition → state
• amount, sum, measure → amount
• degree, quality → degree
• form, shape → form
Another typical issue is the disambiguation of the genus, which consists
on matching words that appear in the definition with their correct sense in the
dictionary. In Amsler (1981) and Chodorow et al. (1985), this task requires human
intervention. Some years later, Bruce and Guthrie (1992) worked on an automatic
procedure to accomplish genus disambiguation. First, they identify the genus of the
definition. Then, they exploit category markups (e.g. plant, solid) and frequency
information to disambiguate the genus with 80% accuracy.
More recently, Navigli (2009a) presented an algorithm to disambiguate words in
dictionary definitions. Their approach is based on the exploitation of circularity in
dictionaries.
Electronic dictionaries are certainly an important source of lexical-semantic
knowledge, but their organisation does not favour their direct use as NLP tools,
since they were made to be read by humans. Wilks et al. (1988) mention several