Automatic Extraction and Validation of Lexical Ontologies from Text

Nowadays, semantic information plays an important role in NLP, more specifically describing and representing the meanings of the words. In the last two decades, there have been efforts to create a large database that represents lexical knowledge. However, in most of the cases, this resources are created manually. For instance Princeton WordNet is considered the standard model of a lexical ontology for the English language. Besides that, also for Portuguese there have been some attempts to create a broad-coverage ontology, also created manually and not publicly available. Still, they are not public available for download, and also all of them were manually created. Despite being less prone to errors, the problem is that the manual creation of these resources takes a lot of time consuming and requires a team, and researchers specialised in the area. Having this in mind, this book describes how to create a system capable of automatically acquire semantic knowledge from any kind of Portuguese text. In addition, it is analysed the benefits from applying similarity distributional metrics based on the occurrence of words in documents to our system outputs.