“The Data Vault Model is a detail oriented, historical tracking and uniquely linked set of normalized tables that support one or more functional areas of business.”Dan Linstedt · Data Vault Series 1 — Data Vault Overview · 2002 · Dan Linstedt, Data Vault Series 1 — Data Vault Overview (2002), definiția modelului
Hub, link, satellite: keys, relations, attributes with history — three kinds of tables, one auditable warehouse.
The star schema is fast to read and easy to understand, but rigid: a new source or a new column means rewriting the dimension. The snowflake normalises the dimensions — fewer duplicates, more joins — and is usually not worth it. Data Vault answers a different problem: how to integrate twenty sources that change often, without rewriting anything and with a full audit trail. Three kinds of tables: hubs (business keys — a customer, a product), links (relations between keys — the customer bought the product) and satellites (descriptive attributes, with load date and source, hence full history). The cost is that a vault is not read directly: it has too many tables. The typical architecture is staging, then vault (raw and business), then star-shaped marts on top for reporting. The choice is not ideological. Few, stable sources: star directly. Many, changing sources with audit requirements: vault underneath, star on top.
Why it matters A warehouse that gets rewritten for every new source never reaches the tenth source. The choice of model decides how cheap change is.