Mumbai University > Information Technology > Sem 5 > Advanced Database Management System

Marks: 10M

Year: Dec 2014

A common way of introducing data warehousing is to refer to the characteristics of a data warehouse as set forth by William Inmon:

• Subject Oriented
• Integrated
• Non-volatile
• Time Variant
• Subject Oriented
  • A data warehouse is subject oriented because it provides information around a subject rather than the organization's ongoing operations.
  • These subjects can be product, customers, suppliers, sales, revenue, etc. A data warehouse does not focus on the ongoing operations, rather it focuses on modelling and analysis of data for decision making.
• Integrated
  • A data warehouse is constructed by integrating data from heterogeneous sources such as relational databases, flat files, etc.
  • This integration enhances the effective analysis of data.
• Time Variant
  • The data collected in a data warehouse is identified with a particular time period.
  • The data in a data warehouse provides information from the historical point of view.
• Non-volatile
  • Non-volatile means the previous data is not erased when new data is added to it.

A data warehouse is kept separate from the operational database and therefore frequent changes in operational database is not reflected in the data warehouse.

The key characteristics of a data warehouse are as follows:

• Some data is denormalized for simplification and to improve performance.
• Queries often retrieve large amounts of data.
• Both planned and ad hoc queries are common.
• The data load is controlled.

In general, high data throughput is the key to a successful data warehouse