Towards open ontology learning and filtering

Open ontology learning is the process of extracting a domain ontology from a knowledge source in an unsupervised way. Due to its unsupervised nature, it requires filtering mechanisms to rate the importance and correctness of the extracted knowledge. This paper presents OntoCmaps, a domain-independent and open ontology learning tool that extracts deep semantic representations from corpora. OntoCmaps generates rich conceptual representations in the form of concept maps and proposes an innovative filtering mechanism based on metrics from graph theory. Our results show that using metrics such as Betweenness, PageRank, Hits and Degree centrality outperforms the results of standard text-based metrics (TF-IDF, term frequency) for concept identification. We propose voting schemes based on these metrics that provide a good performance in relationship identification, which again provides better results (in terms of precision and F-measure) than other traditional metrics such as frequency of co-occurrences. The approach is evaluated against a gold standard and is compared to the ontology learning tool Text2Onto. The OntoCmaps generated ontology is more expressive than Text2Onto ontology especially in conceptual relationships and leads to better results in terms of precision, recall and F-measure.

► We present OntoCmaps, an open ontology learning tool that uses deep NLP methods. ► Our approach is based on patterns and is domain independent. ► We also propose metrics from graph theory to filter important concepts and relationships. ► OntoCmaps results are better than those of another standard ontology learning tool Text2Onto. ► Metrics from graph theory outperform standard text-based metrics usually used such as TF-IDF.