Development Life Cycle

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Development Life Cycle

• Database Design Concepts INFO1408

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Reminder of concept of 3 level architecture in
databases
Forms reports for users
Tables
Storage on disk
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Traditional Method Systems Development Life
Cycle (SDLC)

• Series of phases

You will see variations of this in other text
books these are all equally suitable.
Planning
Requirements gathering
Conceptual/ Logical design
Physical design
Construction
Implementation rollout
Ongoing support
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e.g. SDLC is much the same as the Waterfall
Development Method
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What is involved in the SDLC stages?

• Planning
• Feasibility study
• Form project team
• Review software

Will the project achieve the objective? Will the
budget meet the resource requirements?
Look at different DBMS options. Will it/they do
the job? New s/w? New versions?
Assign Database Administrator (DBA) Set up
initial project team Likely to evolve as
project progresses
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What is involved in the SDLC stages?

• Requirements gathering
• Collect analyse requirements
• Collect analyse user views
• Think of the main entities

What is needed? How is it handled
currently? Various techniques used
i.e. objects of interest In the system
How do we get this info?
Conduct interviews (at all levels) Surveys Observa
tion Document review
Advantages disadvantages of all of all of these
methods on next slides
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Advantages disadvantages of requirements
gathering approaches

• Interviews advantages
• Can get more information than just answers to
  questions and observation of individuals during
  the interview can be informative too.
• Interviews disadvantages
• Can take longer than other methods
• Unskilled interviewer might ask leading questions
  or might respond in a way that leads interviewee
  to answer differently

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Advantages disadvantages of requirements
gathering approaches

• Surveys advantages
• Can gather a lot of information in a short time
• All participants get the same questions in the
  same way
• Surveys disadvantages
• Often have poor response rates
• Hard to compose unbiased questions
• Lose out on benefits of interviews

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Advantages disadvantages of requirements
gathering approaches

• Observation advantages
• See how every day processes are undertaken
• See things as they really are
• Observation disadvantages
• Behaviour can change under observation
• Can take a lot of time in order to be useful
• Can be expensive for various reasons (time,
  travel to other locations etc.)

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Advantages disadvantages of requirements
gathering approaches

• Document review advantages
• Usually less time consuming
• Can give a more complete overview than an
  interview
• Pictures diagrams are usually v. helpful
• Document review disadvantages
• Documents may not reflect practices
• Can be out of date

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Conceptual/Logical Design

• Think about what data the users require to be
  available to them. Consider forms/reports etc.
  Use story boards.
• Determine appropriate entities of the system
• Complete Entity Relationship diagram
• Derive normalised tables from the ERD
• Normalisation process what is this?

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Physical Design

• Decide what hardware and software is to be used
• Decide on processors, disk devices, network
  bandwidth etc.
• Use a DDL (data description language) to create
  the tables indexes. E.g. SQL
• Also use SQL to define storage structures

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Construction Implementation

• Develop the applications programs
• Construct test databases (for testing the
  applications programs)
• Implement the actual database/s required i.e.
  populate with actual data
• User training
• Rollout to users

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Maintenance

• Database performance tuning
• Any S/W patches developed as required
• Make changes to logical model (schema) to support
  required changes in applications
• Monitor disk space

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Advantages Disadvantages of the SDLC/ Waterfall
type methods
Advantages
Disadvantages
Identifies systems requirements long before
programming begins
Design must be specified on paper before
programming begins
Long time between system proposal and delivery
of new system
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Other methods - Prototyping
This is an iterative Process.
Extensive business user Involvement required
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Other methods Rapid Application Development

• Uses 80/20 rule 80 of of the required work can
  be done in 20 of the time
• So might miss out some complicated parts
• Get a working system ready in a short time
• If the process is eventually repeated to complete
  100 of the requirements, the method has become
  closer to prototyping

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Criteria for Selecting the Appropriate Methodology

• Need to consider the following
• Clear user requirements
• Familiar technology
• Complexity
• Reliability
• Time schedule