A Survey of Ontologies and Their Applications in e-Learning Environments

Ontology technology has been investigated in a wide range of areas and is currently being utilized in many fields. In the e-learning context, many studies have used ontology to address problems such as the interoperability in learning objects, modeling and enriching learning resources, and personalizing educational content recommendations. We systematically reviewed research on ontology for e-learning from 2008 to 2020. The review was guided by 3 research questions: "How is ontology used for knowledge modeling in the context of e-learning?", "What are the design principles, building methods, scale, level of semantic richness, and evaluation of current educational ontologies?", and "What are the various ontology-based applications for e-learning?" We classified current educational ontologies into 6 types and analyzed them by 5 measures: design methodology, building routine, scale of ontology, level of semantic richness, and ontology evaluation. Furthermore, we reviewed 4 types of ontology-based e-learning applications and systems. The observations obtained from this survey can benefit researchers in this area and help to guide future research.