If you are working in data warehousing project or going to work on data warehouse project, the two most commonly designed methods are introduced by Ralph Kimball and Bill Inmon. Which advantages / disadvantages of these approaches? Which one is better/ suitable for your business requirement? Lets understand the basic difference between Ralph Kimball and Bill Inmon approaches towards data warehouse.
Bill Inmon: Top-down approach
Bill Inmon, has defined a data warehouse as a centralized repository for the entire enterprise. The top-down approach is designed using a normalized enterprise data model. “Atomic” data, that is, data at the lowest level of detail, are stored in the data warehouse. Dimensional data marts containing data needed for specific business processes or specific departments are created from the data warehouse. In the Inmon vision, the data warehouse is at the center of the “Corporate Information Factory” (CIF), which provides a logical framework for delivering business intelligence (BI) and business management capabilities.
- Subject-oriented: The data in the data warehouse is organized so that all the data elements relating to the same real-world event or object are linked together
- Time-variant: The changes to the data in the database are tracked and recorded so that reports can be produced showing changes over time
- Non-volatile: Data in the data warehouse is never over-written or deleted — once committed, the data is static, read-only, and retained for future reporting
- Integrated: The database contains data from most or all of an organization’s operational applications, and that this data is made consistent
Ralph Kimball: bottom-up approach
Designed an approach to data warehouse design known as bottom-up. In the bottom-up approach, data marts are first created to provide reporting and analytical capabilities for specific business processes.
Data marts contain, primarily, dimensions and facts. Facts can contain either atomic data and, if necessary, summarized data. The single data mart often models a specific business area such as “Sales” or “Production.” These data marts can eventually be integrated to create a comprehensive data warehouse. The data warehouse bus architecture is primarily an implementation of “the bus”, a collection of conformed dimensions and conformed facts, which are dimensions that are shared (in a specific way) between facts in two or more data marts.
Pros and Cos
Compare Ralph Kimbal and Bill Inmon
Decide your approach
Depend on your business requirement, business objectives, nature of business, time and cost involved, and the level of dependencies between various functions \.
Inmon: suitable for stable business which can afford time and cost involved. With each changing business condition, they do not change desing.
Ralph Kimball: the business of organization changes frequently.
Insurance: It is vital to get the overall picture with respect to individual clients, groups, history of claims, mortality rate tendencies, demography, profitability of each plan and agents, etc. All aspects are inter-related and therefore suited for the Inmon’s approach.
Marketing: This is a specialized division, which does not call for enterprise warehouse. Only data marts are required. Hence, Kimball’s approach is suitable.
CRM in banks: The focus is on parameters such as products sold, up-sell and cross-sell at a customer-level. It is not necessary to get an overall picture of the business. For example, there is no need to link a customer’s details to the treasury department dealing with forex transactions and regulations. Since the scope is limited, you can go for Kimball’s method. However, if the entire processes and divisions in the bank are to be linked, the obvious choice isInmon’s design vs. Kimball’s.
Manufacturing: Multiple functions are involved here, irrespective of the budget involved. Thus, where there is a systemic dependency as in this case, an enterprise model is required. Hence Inmon’s method is ideal.
However, as I said all things depend on business requirement, time, cost…in your organization which impact your decision. Ralph Kimball or Bill Inmon is suitable.