@evan @nik Using the OWL Ontology for validation is not ideal for multiple reasons. 1) It's not maintained, 2) it's not complete (only AS2, no AP), 3) it's not fully consistent with normative AS2, 4) it requires RDF, which requires JSON-LD processing of AP messages, 5) if you want message validation, you'll need write code to do something that already exists (SHACL, ShEx). I recommend JSON Schema for plain JSON applications.