  The Multilingual Semantic Web has been in focus for over a decade.
Multilingualism in Linked Data and RDF has shown substantial adoption, but this
is unclear for ontologies since the last review 15 years ago. One of the design
goals for OWL was internationalisation, with the aim that an ontology is usable
across languages and cultures. Much research to improve on multilingual
ontologies has taken place in the meantime, and presumably multilingual linked
data could use multilingual ontologies. Therefore, this review seeks to (i)
elucidate and compare the modelling options for multilingual ontologies, (ii)
examine extant ontologies for their multilingualism, and (iii) evaluate
ontology editors for their ability to manage a multilingual ontology. Nine
different principal approaches for modelling multilinguality in ontologies were
identified, which fall into either of the following approaches: using
multilingual labels, linguistic models, or a mapping-based approach. They are
compared on design by means of an ad hoc visualisation mode of modelling
multilingual information for ontologies, shortcomings, and what issues they aim
to solve. For the ontologies, we extracted production-level and accessible
ontologies from BioPortal and the LOV repositories, which had, at best, 6.77%
and 15.74% multilingual ontologies, respectively, where most of them have only
partial translations and they all use a labels-based approach only. Based on a
set of nine tool requirements for managing multilingual ontologies, the
assessment of seven relevant ontology editors showed that there are significant
gaps in tooling support, with VocBench 3 nearest of meeting them all. This
stock-taking may function as a new baseline and motivate new research
directions for multilingual ontologies.
