The Anatomy of a Semantic Layer
The interactive, foundational tour of the layer you can't see. Watch the direct surface-to-data wiring fork one metric into three numbers, then route it through the semantic layer — and click each part (entities & grain, metrics, relationships, descriptions) to learn what it translates.
Executive Summary
The Way It Was
A data source has a surface you can open — tables, columns, a schema. A BI tool has a surface you can click — dashboards and charts. Because both are visible, we instinctively wire them directly: the dashboard reaches into the warehouse, writes some SQL, and paints a chart. It works for one report. By the tenth, "revenue" means five things and the fiscal calendar is hard-coded in four places — the same metric returns a different number depending on which screen you're on.