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The top-down view allows the selection of the relevant information necessary for the
data warehouse. This information matches current and future business needs.
The data source view exposes the information being captured, stored, and man-
aged by operational systems. This information may be documented at various levels
of detail and accuracy, from individual data source tables to integrated data source
tables. Data sources are often modeled by traditional data modeling techniques, such
as the entity-relationship model or CASE (computer-aided software engineering)
tools.
The data warehouse view includes fact tables and dimension tables. It represents the
information that is stored inside the data warehouse, including precalculated totals
and counts, as well as information regarding the source, date, and time of origin,
added to provide historical context.
Finally, the business query view is the data perspective in the data warehouse from
the end-user’s viewpoint.

Building and using a data warehouse is a complex task because it requires business
skills, technology skills, and program management skills. Regarding business skills, building
a data warehouse involves understanding how systems store and manage their data, how
to build extractors that transfer data from the operational system to the data warehouse,
and how to build warehouse refresh software that keeps the data warehouse reasonably
up-to-date with the operational system’s data. Using a data warehouse involves under-
standing the significance of the data it contains, as well as understanding and translating
the business requirements into queries that can be satisfied by the data warehouse.
Regarding technology skills, data analysts are required to understand how to make
assessments from quantitative information and derive facts based on conclusions from
historic information in the data warehouse. These skills include the ability to discover
patterns and trends, to extrapolate trends based on history and look for anomalies or
paradigm shifts, and to present coherent managerial recommendations based on such
analysis. Finally, program management skills involve the need to interface with many
technologies, vendors, and end-users in order to deliver results in a timely and cost-
effective manner.

4.3.2 Data Warehouse Design Process
Let’s look at various approaches to the data warehouse design process and the steps
involved.
A data warehouse can be built using a top-down approach, a bottom-up approach,
or a combination of both. The top-down approach starts with overall design and plan-
ning. It is useful in cases where the technology is mature and well known, and where
the business problems that must be solved are clear and well understood. The bottom-
up approach starts with experiments and prototypes. This is useful in the early stage
of business modeling and technology development. It allows an organization to move