Since a data warehouse reflects the business model of an
enterprise, an essential element of a warehousing architecture
is metadata management. Many different kinds of metadata
have to be managed. Administrative metadata includes all of
the information necessary for setting up and using a
warehouse: descriptions of the source databases, back-end
and front-end tools; definitions of the warehouse schema,
derived data, dimensions and hierarchies, predefined queries
and reports; data mart locations and contents; physical
organization such as data partitions; data extraction, cleaning,
and transformation rules; data refresh and purging policies;
and user profiles, user authorization and access control
policies. Business metadata includes business terms and
definitions, ownership of the data, and charging policies.
Operational metadata includes information that is collected
during the operation of the warehouse: the lineage of
migrated and transformed data; the currency of data in the
warehouse (active, archived or purged); and monitoring
information such as usage statistics, error reports, and audit
trails.