ORIGINAL PAPER ECO and Onto.PT: a flexible approach for creating a Portuguese wordnet automatically Hugo Gonçalo Oliveira · Paulo Gomes Published online: 4 September 2013 © Springer Science+Business Media Dordrecht 2013 Abstract A wordnet is an important tool for developing natural language pro- cessing applications for a language. However, most wordnets are handcrafted by experts, which limits their growth. In this article, we propose an automatic approach to create wordnets by exploiting textual resources, dubbed ECO. After extracting semantic relation instances, identified by discriminating textual patterns, ECO discovers synonymy clusters, used as synsets, and attaches the remaining relations to suitable synsets. Besides introducing each step of ECO, we report on how it was implemented to create Onto.PT, a public lexical ontology for Portuguese. Onto.PT is the result of the automatic exploitation of Portuguese dictionaries and thesauri, and it aims to minimise the main limitations of existing Portuguese lexical knowledge bases. Keywords Information extraction · Lexical ontology · Wordnet · Clustering · Semantic relations 1 Introduction A substantial amount of data produced every day is available in natural language text. Understanding its meaning involves more than recognising words and their interactions, and typically requires access to external sources of knowledge. This fact lead to the creation of broad-coverage knowledge bases, which can be exploited H. Gonçalo Oliveira (&) · P. Gomes CISUC, Departamento de Engenharia Informa ´tica, Faculdade de Cie ˆncias e Tecnologia, Universidade de Coimbra, Po ´lo II, Pinhal de Marrocos, 3030-290 Coimbra, Portugal e-mail: hroliv@dei.uc.pt P. Gomes e-mail: pgomes@dei.uc.pt 123 Lang Resources & Evaluation (2014) 48:373-393 DOI 10.1007/s10579-013-9249-9