See: https://materialdigital.github.io/pmdkg/
The PMD Knowledge Graph enables exploration of the ontological framework based on PMDco v2.0.7, along with compatible application ontologies and alternative frameworks developed within the MaterialDigital Initiative. Using predefined SPARQL queries, everyone can investigate the T-Boxes of the named graphs.
The knowledge graph contains the various MaterialDigital application ontologies contributed by different projects and the PMD application ontologies.