Web Annotation Model and Web Annotation Protocol specify an approach to express annotations (including commentary, review, etc.) and an associated protocol to create and manage them. Annotations are expressed using an RDF-based vocabulary and can be rendered as JSON-LD. The protocol is based on HTTP and adheres to REST design principles. https://www.w3.org/TR/annotation-model/ ; https://www.w3.org/TR/annotation-protocol/