21.4 Data Layers & Modeling Zones
A layered architecture prevents raw acquisition logic, business semantics and consumption-specific calculations from becoming one tangled model.
Recommended logical layers
1. Acquisition
Purpose: land or access source-aligned data.
2. Harmonization
Purpose: standardize keys, types, reference data and integration logic.
3. Semantic
Purpose: define reusable facts, dimensions, measures and business meaning.
4. Consumption
Purpose: expose focused analytical models and consumer-specific contracts.
5. Product
Purpose: package governed, discoverable reusable data for broader consumption.
These are logical responsibilities, not mandatory physical layers or separate spaces.
Grain discipline
Every fact-like entity must state its grain.
Example: One row = one purchase-order item.
Never mix grains casually inside a model.
Anti-pattern
Raw + transformation + semantic + dashboard logic inside one giant view.
It becomes difficult to test, reuse, optimize and govern.
Architect rule
Layer when responsibility changes, not merely because a diagram has room for another box.