Recent progress on geologic time ontologies and considerations for future works

Semantic Web technologies bring innovative ideas to computer applications in geoscience. As an essential part of the Semantic Web, ontologies are increasingly discussed in the geoscience community, in which geologic time scale is one of the topics that have received the most discussion and practices. This paper aims to carry out a review of the recent progress on geologic time ontologies, discuss further improvements, and make recommendations for other geoscience ontology works. Several models and ontologies of geologic time scale are collected and analyzed. Items such as ontology evaluation, ontology mapping, ontology governance, ontology delivery and multilingual labels are discussed for advancing the geologic time ontologies. We hope the discussion can be useful for other geoscience ontology works, and we also make a few further recommendations, such as referring to an ontology spectrum in ontology creation, collaborative working to improve interoperability, and balancing expressivity, implementability and maintainability to achieve better applications of ontologies.