  Ontologies are a popular way of representing domain knowledge, in particular,
knowledge in domains related to life sciences. (Semi-)automating the process of
building an ontology has attracted researchers from different communities into
a field called "Ontology Learning". We provide a formal specification of the
exact and the probably approximately correct learning models from computational
learning theory. Then, we recall from the literature complexity results for
learning lightweight description logic (DL) ontologies in these models.
Finally, we highlight other approaches proposed in the literature for learning
DL ontologies.
