Presentation about usability of linked data, following LODLAM 2020 at the Getty. Discusses JSON-LD 1.1, IIIF, Linked Art, in the context of the design principles for building usable APIs on top of semantically accurate models, and domain specific vocabularies. In particular a focus on the different abstraction layers between conceptual model, ontology, vocabulary, and application profile and the various uses of the data.