Transcript Problems to Consider

Data Warehousing: A Definition
• “A data warehouse is a single integrated store of data
which provides the infrastructural basis for
informational applications in the enterprise”
Kelly, “Data Warehousing”, p55
• Will be a collection of tools - not just a database
– query system to support decision making
– Ability to trawl (mine) in a way that suits the user
– integrated store of consistent, up to date data
• Main aim to maximise the effective use of data within a
business.
• Create a bridge between disparate systems
Data Warehousing
Old Rationale for IS
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Automate the business process
reduce costs
Information seen as a fortuitous by-product
Emphasis on IS as a input/processing/output
– define functions
– specify what system does
– difficult to change outputs
Data Warehousing
Problems With a Data Processing Approach
• Data problems
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resident in different systems
inconsistent
different attributes
different time bands/frames
irreconcilable
Deletion vs. archiving of data
inappropriate and inconsistent data models
Data Warehousing
Issues in Moving to Data Warehousing Philosophy
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Ownership issues
Planning across department/functional areas
Economic issues
Standardisation of data model
– similar data entities in multiple systems
– data inextricably bound with application
• Standards in application design
– piecemeal approaches to system implementation
• Multiple interpretations of reality
Data Warehousing
The Business Case for Data Warehousing
• Reduce costs (?)
• Increase business e.g. through better
understanding of customers
• Develop competitive advantage
• Change the nature of the business
Data Warehousing
Advantages of Data Warehousing
• Removes query and reporting load from TPS
• Allows more appropriate technology for queries
and reports
• Provides a more simple query interface to users
• May provide a higher integrity DB than a TPS
• Easy way of reporting across multiple systems
• May provide a DB with a longer memory than a
TPS!
• May make TPS more secure by reducing access
Data Warehousing
Disadvantages of Data Warehousing
• May rely too heavily on data generated only from TPS
• May complicate business processes by
“institutionalising” reports, data for data’s sake
• Learning curve too long - technical and business aspects
• Culture of developing quick and dirty strategic
applications
• End-users may not have skills for building queries
• Availability of data warehousing skills
• Data warehouses require high maintenance
• Cost of information may outweigh its benefit
Data Warehousing
Problems to Consider
• Extracting, cleaning and loading of data may be time consuming
• Undetected error in systems feeding the warehouse
• Warehouse project may highlight unrecorded data in existing
systems
• End user training in query and reporting tools may increase
requests for IS written reports
• End user approaches to calculations may differ due to different
business views
• Creation of a large-scale data warehouse may homogenise data reducing content
• Conflict between “need to know” and “right to know” mindsets
Data Warehousing
Data Warehousing Tools
• Meta-data modelling
• Data transformation
– Extract
– Cleanse
– Load
• Database (relational, parallel)
• Query language
Data Warehousing
Relationship Between Data Warehouse and Other Systems
User
Application
Information Retrieval
Application
Data
Warehouse
Application
Importing
Process
Periodic transformation
And integration process
TPS
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TPS
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TPS
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Data Warehousing
Some Political Issues (IS)
• Who should a data warehousing development group
report to?
• Who should administrate over the warehouse? (DBS or
development group)
• How should the support of feeder system developers be
gained? What about errors in the feeder system?
• Who has responsibility for data quality monitoring?
• What about changes to the feeder systems?
Data Warehousing
Some Political Issues (User-IS)
• Why should users give up control of
user managed databases?
• How is the co-operation gained of a user
who’s spreadsheet is being automated?
• Should design be for the needs of the
masses or the most demanding users?
• How many data marts should there be?
Data Warehousing
Some Political Issues (User-User)
• Who has access to what data?
• Do all users define and interpret data the
same way?
• Who has the final say about the
“correctness” of data
Data Warehousing
General Political Issues
• Imposes new obligations whose
responsibilities are unclear.
• May require a change in processes that
an organisation may not be comfortable
with.
• Requires agreement on some and not all
definitions of data
Data Warehousing
Some Useful References...
• Http://pwp.starnetinc.com/larryg
• Kelly, (1998) “Data Warehousing”,
Wiley
Data Warehousing