Dw: The Choice Of Inmon Versus Kimball

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Data Warehouse:
The Choice of
Inmon versus Kimball
Ian Abramson
IAS Inc.

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Agenda
The 2 Approaches
Bill Inmon – Enterprise Warehouse (CIF)
Ralph Kimball – Dimensional Design

Similarities
Differences
Choices

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DW History
1990
Inmon publishes “Building the Data Warehouse”

1996
Kimball publishes “The Data Warehouse Toolkit”

2002
Inmonupdates book and 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

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The Data Warehouse Is:
Bill Inmon, an early and influential practitioner,has formally defined a
data warehouse in the following terms;
Subject-oriented
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;

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 databaseis never over-written or deleted - once committed, the data
is static, read-only, but retained for future reporting; and

Integrated
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 adata
warehouse:
“A copy of transaction data specifically structured for query and analysis.“
Ref: wikipedia

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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 abottom-up data warehousing methodology 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 datawarehouse should be
designed from the top-down to include all corporate data. In this
methodology, data marts are created only after the complete data
warehouse has been created.

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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 thecomplete organizational view
of information needed to run and understand
the business

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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
Generallysmaller, selected facts and dimensions
Integrated

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Data Warehouses vs.
Data Marts
Data Warehouses:
Scope
Application independent
Centralized or Enterprise
Planned

Data
Historical, detailed, summary
Some denormalization

Subjects
Multiple subjects

Source
Many internal and external sources

Other
Flexible
Data oriented
Long life
Single complex structure
8Data Marts:
Scope
Specific application
Decentralized by group
Organic but may be planned

Data
Some history, detailed, summary
High denormalization

Subjects
Single central subject area

Source
Few internal and external sources

Other
Restrictive
Project oriented
Short life
Multiple simple structures that may
form a complex structure

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The Inmon Model
Consists...