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

8 Chapter 1. Introduction
Chapter 5 describes how synonymy networks extracted, for instance, from dictionaries,
may be exploited in the discovery of synsets. To this end, a clustering
procedure is ran on the previous networks and the discovered clusters are used as
synsets. The clustering algorithm actually discovers fuzzy synsets, where a weight
is associated to the membership of a word to a synset, in a more realistic representation
of words and meanings. This part of the work led to the creation of the
Portuguese fuzzy thesaurus, CLIP, completely extracted from dictionaries.
Chapter 6 presents an approach for enriching the synsets of a thesaurus
with synonymy relations extracted from dictionaries. Given that there are
freely available synset-based resources for Portuguese, we decided to exploit them in
the creation of Onto.PT. Therefore, we used a public handcrafted thesaurus as the
starting point for the creation of a broader synset-base. First, synonymy instances
are assigned to the most similar synset. Then, the relations not assigned to a synset
are the target of clustering, to discover new synsets, later added to the synsetbase.
This part of the work originated TRIP, a large synset-based thesaurus of
Portuguese.
Chapter 7 proposes several algorithms for moving from term-based semantic
relations to relations held between the synsets of a wordnet. After establishing
the synset-base of Onto.PT, we still had a lexical network with semantic relations
held between terms, and not synsets. Therefore, we developed and compared a set
of algorithms that take advantage of the lexical network, and of the lexical items
in the synsets, to select suitable synsets for attaching each argument of the lexical
network’s relations. Given a synset-base and a lexical network, the result of these
algorithms is a wordnet.
Chapter 8 summarises the work described in the previous chapters, which may
be combined in ECO, the automatic approach for creating Onto.PT, a new lexical
ontology for Portuguese. An overview of this resource is first presented, together
with some details on its availability, and on its evaluation. The last section suggests
possible scenarios where Onto.PT might be useful.
Chapter 9 presents a final discussion on this research and highlights its main contributions.
In the end, some cues are given for further improvements and additional
work.