GWC 2008

SemanticNet: a WordNet-based Tool for the Navigation of Semantic… 23
also extract the specialized semantics keys from the structured part of a document and
return the generic semantic key mapped to these keys by means of the conceptual
mapping.
Unstructured parts need a linguistic analysis and a semantic interpretation to be
performed by means of NLP techniques. The main tools involved are:
• the Syntactic Analyzer and Disambiguator, a module for the syntactic analysis,
integrated with the Link Grammar parser [6], a highly lexical, context-free
formalism. This module identifies the syntactical structure of sentences, and
resolves the terms' roles ambiguity in natural languages;
• the Semantic Analyzer and Disambiguator, a module that analyzes each
sentence identifying roles, meanings of terms and semantic relations in order to
extract “part of speech” information, the synonymy and hypernym relations
from the WordNet semantic net. It also evaluates terms contained in the
document by means of a density function based on the synonyms and
hypernyms frequency [7];
• the Classifier, a module that classifies documents automatically. As proposed in
WordNet Domains ([8] and [9]), a lexical resource representing domain
associations between terms, the module applies a classification algorithm based
on the Dewey Decimal Classification (DDC) and associates a set of categories
and a weight to each document.
The analysis of structured parts, followed by the linguistic analysis and the semantic
interpretation of unstructured parts, produces as results three types of semantic keys:
• a synset ID identifying a particular sense of a term of WordNet
• a category name given by a possible classification
• a key composed by a word and a document category, i.e. when the semantic key
related to the word is not included in the WordNet vocabulary.
Finally, all semantic keys are used to index the document whereas in searching
phase they are used in order to retrieve document descriptors using the SemanticNet
through the concept of semantic vicinity.
2.2 The Specific Context
In a specific context the system adopts a formal or terminological ontology describing
the specific semantic domain. The semantic keys are the identifiers of concepts in the
specialized ontology and the classification is performed using the taxonomy defined
in it.
Different analysis are performed in structured and unstructured parts of the
document, as identified in the generic context. Moreover two types of indexing are
performed: one with a set of generic semantic keys and the other with a set of
specialized semantic keys.
The module extracts all of the specialized semantic keys each time a structured part
related to a specific context is identified in a document. Otherwise the system