Bill Inmon is a first author of data warehouse system concept and introduced “Enterprise Data Architecture” based on Normalization Technique.
Inmon vision is Data warehouse is centralized repository of “Corporate Information Factory” (CIF), which provides a Logical Framework for delivering Business Intelligence (BI) and Business Management Capabilities.
“Atomic” data is lowest level of detail that stored in the Data warehouse and then builds Data Marts based on Subjective of Enterprise Operation or Entity. This is called “Top to Bottom” Data warehouse Design Methodology.
Inmon states that the data warehouse is:
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.
Data in the data warehouse are never over-written or deleted — once committed, the data are static, read-only, and retained for future reporting.
The data warehouse contains data from most or all of an organization's operational systems and these data are made consistent.
The top-down design methodology generates highly consistent dimensional views of data across data marts since all data marts are loaded from the centralized repository. Top-down design has also proven to be robust against business changes. Generating new dimensional data marts against the data stored in the data warehouse is a relatively simple task. The main disadvantage to the top-down methodology is that it represents a very large project with a very broad scope. The up-front cost for implementing a data warehouse using the top-down methodology is significant, and the duration of time from the start of project to the point that end users experience initial benefits can be substantial. In addition, the top-down methodology can be inflexible and unresponsive to changing departmental needs during the implementation phases.
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