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

1.4. Outline of the thesis 7
which can be seen as another contribution of this thesis, enabled us to use the same
grammars for extracting information from three dictionaries.
Together with Onto.PT, other lexical-semantic resources were developed by using
each of the ECO steps independently. These resources, listed below, contribute for
advancing the state-of-the-art of Portuguese LKBs:
• CARTÃO, the largest term-based lexical-semantic network for Portuguese;
• CLIP, as far as we know, the first broad-coverage fuzzy thesaurus for Portuguese;
• TRIP, the largest public synset-based thesaurus for Portuguese.
We should add that most of the work performed during the course of this thesis is
reported in a total of 14 scientific papers, presented and/or published in national and
international venues, such as IJCAI, ECAI, EPIA or NLDB (see more in section 9.1).
1.4 Outline of the thesis
After two chapters on background knowledge and related work, each chapter of this
thesis is focused on an automatic procedure that integrates the ECO approach and
performs one step towards our final goal, the creation of Onto.PT. Besides describing
each procedure, one or more experiments towards its validation are reported in each
chapter. Before concluding, the last version of Onto.PT, available while this thesis
was written, is presented together with examples of scenarios where it might be
useful. In the end of the thesis, two appendices were included, namely: (A), with an
extensive list of the semantic relations in Onto.PT and their description; and (B),
which shows a rough manual mapping between the Onto.PT synsets and the core
concepts of Princeton WordNet. We now describe each chapter, briefly:
Chapter 2 introduces (mostly) theoretical background knowledge that supports
this research. It starts with some remarks on lexical semantics, the subfield
of semantics that deals with words and meanings. Then, different formalisms for
representing lexical-semantic computational resources are described. Given that
our work is related to the NLP field of information extraction, the last section is
dedicated to this topic.
Chapter 3 is about concrete work with some relation to our research. First, it
describes well-known lexical knowledge bases for English, and also for Portuguese.
Second, it presents work on information extraction from dictionaries and also from
corpora. Third, work on the automatic enrichment or integration of existing knowledge
bases is referred.
Chapter 4 explains our work towards the acquisition of semantic relations
from dictionaries. As many regularities are kept across definitions in different
dictionaries, we reuse existing handcrafted grammars, made for the extraction of
semantic relations from one dictionary, for extracting relations from other dictionaries.
This results in CARTÃO, a large lexical network for Portuguese that
integrates knowledge from three different dictionaries.