sdd:Diagram
A sdd:Diagram is the class of the @diagram construct — the root of a scene (design spec §2). It extends Claim and Query: a diagram may cite facts from zero or more sources with claim provenance discipline, assert new facts as its own contribution, and dress the resulting facts visually. Both the cited and asserted sets may be empty — a purely visual diagram is legal — and a published diagram is itself a source others can claim from.
A diagram's dataset partitions into three classes (spec §3.1): factual quads (cited or asserted), structural-visual quads (the derived scene — never authored), and aesthetic quads (geometry and decoration). sdd:diagramType selects the diagram's genre, for example sdd:BlockDiagram; sdd:hasScope points at the diagram's scopes, at minimum a sdd:LocalScope for its asserted facts. The scene the diagram dresses is built from sdd:Node, sdd:Edge, and sdd:Datum instances.