Data Warehouse: The Choice of Inmon versus Kimball
Ian Abramson IAS Inc.
The 2 Approaches
Bill Inmon – Enterprise Warehouse (CIF) Ralph Kimball – Dimensional Design
Similarities Differences Choices
Inmon publishes “Building the Data Warehouse”
Kimball publishes “The Data Warehouse Toolkit”
Inmon updates bookand defines architecture for collection of disparate sources into detailed, time variant data store.
The top down approach
Kimball updates book and defines multiple databases called data marts that are organized by business processes, but use enterprise standard data bus
The bottom-up approach
The Data Warehouse Is:
Bill Inmon, an early and influential practitioner, hasformally defined a data warehouse in the following terms;
The data in the database is organized so that all the data elements relating to the same real-world event or object are linked together;
The changes to the data in the database are tracked and recorded so that reports can be produced showing changes over time;
Data in the database is neverover-written or deleted - once committed, the data is static, read-only, but retained for future reporting; and
The database contains data from most or all of an organization's operational applications, and that this data is made consistent
Ralph Kimball, a leading proponent of the dimensional approach to building data warehouses, provides a succinct definition for a data warehouse:“A copy of transaction data specifically structured for query and analysis.“
What are they saying?
These two influential data warehousing experts represent the current prevailing views on data warehousing. Kimball, in 1997, stated that
"...the data warehouse is nothing more than the union of all the data marts", Kimball indicates a bottom-up data warehousingmethodology in which individual data marts providing thin views into the organizational data could be created and later combined into a larger all-encompassing data warehouse.
Inmon responded in 1998 by saying,
"You can catch all the minnows in the ocean and stack them together and they still do not make a whale," This indicates the opposing view that the data warehouse should be designedfrom the top-down to include all corporate data. In this methodology, data marts are created only after the complete data warehouse has been created.
What is a Data Warehouse:
The single organizational repository of enterprise wide data across many or all lines of business and subject areas.
Contains massive and integrated data Represents the complete organizational view ofinformation needed to run and understand the business
What is a Data Mart?
The specific, subject oriented, or departmental view of information from the organization. Generally these are built to satisfy user requirements for information
Multiple data marts for one organization A data mart is built using dimensional modeling More focused Generally smaller, selected facts and dimensionsIntegrated
Data Warehouses vs. Data Marts
Application independent Centralized or Enterprise Planned
Specific application Decentralized by group Organic but may be planned
Historical, detailed, summary Some denormalization
Some history, detailed, summary High denormalization
SubjectsSingle central subject area
Many internal and external sources
Few internal and external sources
Flexible Data oriented Long life Single complex structure
Restrictive Project oriented Short life Multiple simple structures that may form a complex structure
The Inmon Model
Consists of all databases and information systems in an...
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