Hi there, I'm doing some research about ontology in moodle for a some learning analytics proyect. Maybe this papers can help:
Extending Moodle Functionalities with Ontology-based Competency Management
https://www.sciencedirect.com/science/article/pii/S187705091401103X
https://www.researchgate.net/publication/261265752_Ontology_of_moodle_e-learning_system_for_social_network_analysis