Annotation (CDS)
What it is
Metadata attached to a CDS entity or field (`@UI`, `@Semantics`, `@ObjectModel`, `@OData`…) that downstream consumers read — Fiori Elements builds the UI, OData exposes semantics, analytics interprets measures. Declarative, not procedural.
Why it matters for Clean Core
Annotations are how a RAP/Fiori Elements app gets its UI 'for free' — list columns, object pages, value helps — from the data model. Mastering @UI annotations is most of building a Fiori Elements app.
Common pitfall
Scattering @UI annotations across the interface (engine) view instead of keeping them on the projection (consumption) view. Keep consumption-specific UI metadata on the projection so the reusable interface stays clean.