Data warehouse – Kimball or Inmon model.
The following information provides an understanding of the basics of two different approach in Data warehouse modeling:
History of Data Warehouse:
In 1990 Inmon wrote a book “Building the Data Warehouse.”
Inmon defines an architecture for the collection of disparate sources into detailed, time variant data store (The top-down approach).
In 1996 Kimball wrote “The Data Warehouse Toolkit.”
Kimball updates the book and defines multiple databases called data-marts that are organized by business processes but use Data bus architecture (The bottom-up approach).
Data Warehouse VS Data Mart:
A Data warehouse is a collection of Enterprise-wide data across the line of business and subject areas. Data is integrated using a massive database. Provides a complete organizational view of the information needed to run the business.
A Data mart offers the departmental view of information specific and subject-oriented. Build multiple data-marts using dimensional architecture. Provides Fact-based information integrated with various dimensions.
- As per Bill Inmon, a data warehouse is a subject-oriented data repository and the data in the database organized with data elements relating and linking together.
- Time-variant: The changes to the data in the database tracked and recorded showing changes over time.
- Non-volatile: Data in the database is never over-written or deleted – once committed, the data is static, read-only, but retained for future, and for maintaining the history.
- Database: The database contains data from all operational applications, and the data is made consistent for reporting purpose.
- The data warehouse should be designed from the top-down to include all corporate data. In this methodology, data marts created after the complete data warehouse creation.
- Ralph Kimball is the proponent of the dimensional modeling and approach to building data warehouse through data marts.
- As per Kimball, the data warehouse is nothing more than the union of all the data-marts. Kimball indicates a bottom-up approach for data warehousing, by creating individual data marts are created providing views into the organizational data in chunks
- Eventually, an Enterprise Data warehouse built by combining the data marts using Bus architecture.
Inmon VS Kimball: