A conformed dimension is a dimension built once and reused consistently across multiple fact tables or subject areas. Same grain of entity, same key, same attribute definitions.
A local dimension is used by only one fact or mart and is not shared (or not standardized) elsewhere.
Conformed: dim_date, dim_customer used by fct_orders, fct_shipments, fct_support_tickets Local: dim_ticket_priority used only by support mart
Why conformity matters
If dim_customer in sales means "billing account" and in marketing means "cookie profile," cross-domain dashboards lie. Conformed dims give one meaning for customer_sk.
How you get there
- Shared
dim_datewith company calendar rules - Master customer dimension with agreed natural key
- Governance: one owner for the conformed model
Interview tip
> "Conformed = same dimension, same meaning, reusable across facts. Local = mart-specific."