Base De Datos

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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
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

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The Data Warehouse Is:
Bill Inmon, an early and influential practitioner, hasformally 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 database is neverover-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 a data 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 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.

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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 the complete organizational view ofinformation 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 Generally smaller, selected facts and dimensionsIntegrated

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

Data Marts:
Scope
Specific application Decentralized by group Organic but may be planned

Data
Historical, detailed, summary Some denormalization

Data
Some history, detailed, summary High denormalization

Subjects
Multiple subjects

SubjectsSingle central subject area

Source
Many internal and external sources

Source
Few internal and external sources

Other
Flexible Data oriented Long life Single complex structure
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Other
Restrictive Project oriented Short life Multiple simple structures that may form a complex structure

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The Inmon Model
Consists of all databases and information systems in an...