Building the Data WareHouse

1. Building Data WareHouse
by Inmon
Chapter 09: Migration to the Architected Environment
http://it-slideshares.blogspot.com

2. 9. Migration to the Architected
Environment
1. A Migration Plan
2. The Feedback Loop
3. Strategic Considerations
4. Methodology and Migration
5. Summary
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3. 9.1 A Migration Plan
 Beginning point: Data Model -
represents the information needs of
the corporation.
 Data Model needs to identify at a
minimum:
◦ Major subjects of the corporation
◦ Definition of the major subjects of the
corporation
◦ Relationships between the major subjects
◦ Groupings of keys and attributes that
more fully represent the major subjects

4. 9.1 A Migration Plan (ct.)
 After having the corporate data
model, the next activity is defining the
system of record.
 It is nothing more than the identification
of the “best” data that the corporation
has:
◦ Most timely
◦ Most accurate
◦ Most complete
◦ Nearest to the external source
◦ Most structurally compatible

5. 9.1 A Migration Plan (ct.)

6. 9.1 A Migration Plan (ct.)
 Technological challenges in bringing
the system-of-record data into the
DW:
◦ A change in DBMS
◦ A change in operating systems
◦ The need to merge data from different
DBMSs and operating systems
◦ The capture of the Web-based data in the
Web logs
◦ A change in basic data formats

7. 9.1 A Migration Plan (ct.)
 After the system of record is defined, the
next step is to design the data
warehouse.
 The following things need to be done:
◦ An element of time needs to be added to the
key structure if one is not already present.
◦ All purely operational data needs to be
eliminated.
◦ Referential integrity relationships need to be
turned into artifacts.
◦ Derived data that is frequently needed is
added to the design.

8. 9.1 A Migration Plan (ct.)

9. 9.1 A Migration Plan (ct.)
 After the data warehouse is
designed, the next step is to design and
build the interfaces between the system
of record and the DW.
 Interfaces’ activities:
◦ Being an extract process
◦ Integration of data from the
operational, application-oriented environment
◦ Alteration of the time basis of data
◦ Condensation of data
◦ Efficient scanning of the existing systems
environment

10. 9.1 A Migration Plan (ct.)
 Once the interface programs are
designed and built, the next activity is
to start the population of the first
subject area:
◦ The first of the data is read in the legacy
environment; and then it is captured and
transported to the data warehouse
environment.
◦ Directories are updated
◦ Metadata is created
◦ Indexes are made
http://it-slideshares.blogspot.com

11. 9.1 A Migration Plan (ct.)
 Caution: If you
wait for existing
systems to be
cleaned up, you
will never build a
data warehouse

12. 9.2 The Feedback Loop
 At the heart of success in the long-term
development of the data warehouse is the
feedback loop between the data architect and
the DSS analyst.
 The DSS analyst:
◦ uses the data warehouse as a basis for
analysis
◦ conveys those requirements to the data
architect
 The data architect:
◦ add data, delete data, alter data, and so forth
based on the recommendations of the DSS
analyst
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13. 9.2 The Feedback Loop
(ct.)
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14. 9.3 Strategic
Considerations
 The DW
environment is
designed and built
for the purpose of
supporting the DSS
needs of the
organization.
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15. 9.3 Strategic Considerations
(ct.)
 Besides that, the
corporation has
operational needs
as well.
 But the
operational world
is shown as being
in a state of
chaos.
http://it-slideshares.blogspot.com

16. 9.3 Strategic Considerations
(ct.)
 The steps the data architect takes to
restructure the operational
environment:
◦ Create a ‘delta’ list
◦ The impact analysis
◦ Create the resource estimate
◦ All the preceding are packaged in a report
that goes to information systems
management.
http://it-slideshares.blogspot.com

17. 9.3 Strategic Considerations
(ct.)
 Operation cleanup plan:

18. 9.4 Methodology and Migration
 The methodology for the building of
the data warehouse is called a spiral
development methodology.
 The spiral methodology not only
contains information about how to
build a data warehouse, but also
describes how to use the data
warehouse.
http://it-slideshares.blogspot.com

19. 9.4 Methodology and Migration
(ct.)
 The differences between the waterfall
approach and the spiral approach:

20. 9.5 Summary
 The starting point for the design of the data
warehouse is the corporate data model,.
 The data warehouse is built iteratively.
 The development approach for the data
warehouse environment is said to be an
iterative or a spiral development approach.
 The feedback loop between the data
architect and the end user is an important
part of the migration process.
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