A Survey of Ontology Learning Procedures Lucas Drumond and Rosario Girardi Federal University of Maranh˜ao, Computer Science Department, Av. dos Portugueses, S˜ao Lu´ ıs, Brasil ldrumond@gmail.com,rgirardi@deinf.ufma.br http://gesec.deinf.ufma.br Abstract. Ontologies constitute an approach for knowledge represen- tation that can be shared establishing a shared vocabulary for different applications and are also the backbone of the Semantic Web. Thus a fast and efficient ontology development is a requirement for the suc- cess of many knowledge based systems and for the Semantic Web itself. However, ontology development is a difficult and time consuming task. Ontology learning is an approach for the problem of knowledge acquisi- tion bottleneck that aims at reducing the cost of ontology construction through the development of automatic methods for the extraction of knowledge about a specific domain and its representation in an ontol- ogy like structure. This paper provides a discussion on existing ontology learning techniques and the state of the art of the field. Key words: Ontologies; Ontology Learning; Machine Learning; Knowl- edge Acquisition 1 Introduction Ontologies constitute an approach for knowledge representation that is capable of expressing a set of entities and their relationships, constraints, axioms and the vocabulary of a given domain. An ontology should be machine readable in such a way that information systems are able to use them to represent and share the knowledge about the application domain. Ontologies hold a great importance to modern knowledge based systems. For instance, they constitute a powerful tool for supporting natural language pro- cessing [1][2][3], information filtering [4][5], information retrieval [6] and data access [7]. Besides, they also provide a formalism for specifying similarity mea- sures which have presented good effectiveness [8][5][9]. One of the greatest application of ontologies is the Semantic Web [10][11], a new generation of the Web in which the semantic of documents, in most cases currently expressed only in natural language, would be expressed using ontolo- gies. This way, the Semantic Web is an approach for enhancing the effectiveness of Web information access. However, the manual construction of ontologies is an expensive and time- consuming task because the professionals required for this task (i.e. a domain