sdd:uses
sdd:uses imports a template or mapping document into a sdd:Diagram. Its objects are document IRIs — packages from the diagram library (spec §1): alignment axioms binding world vocabulary to the visual domain, plus node/edge templates for a given diagram type.
sdd:uses is how a diagram's authored DSL stays declarative rather than pasting template logic inline: uses <../diagram-templates/plant> at the top of a @diagram block names the mapping the source blocks below are compiled against. In later plans, the imported documents are exactly what the derive(F, O) compilation (spec §3.5) reads to turn cited facts into scene quads — sdd:uses names O.