The lifecycle model

offbeatnothingSoftware and s/w Development

Dec 2, 2013 (3 years and 4 months ago)

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The lifecycle model

Maintenance
Installation
Feasibility
Study
Design
Analysis
Programming
Systems development life cycle

(the ‘Waterfall model’)


Post-
implementation
review
Conversion
Coding and
testing
Design
Requirements
Analysis
Feasibility
study
Analysis
Design
Implementation
Review and
Maintenance

In the waterfall model, it is possible to rework earlier
stages in the light of experience gained at a later
stage. Each stage is signed off and the next stage is
proceeded with. However the end user is rarely
involved in the development stage, even though they
may well be involved in signing off. It is therefore
critical that the analysts and the programmers
understand the end
-
users’ requirements. This can be
quite difficult with the waterfall model.


Using the waterfall model

Prototyping


The waterfall model has disadvantages, which can be
overcome using Prototyping, in which a model of the
system is developed in partnership with the end
-
user.
The features are worked out with the end user using a
prototype, and the end user can have a considerable
input into the development of a project.

Prototyping

Establish an
outline
specification
Design and
implement
system
Specify
Evaluate
Develop a
prototype
Benefits of prototyping


Misunderstandings between software developers and
users can be identified;


Missing functions may be detected;


Incomplete or inconsistent user requirements may be
detected;


A prototype version will be quickly available to
demonstrate the feasibility to management;


The prototype can sometimes be used for training
before the final system is delivered

Drawbacks of prototyping


Project management can be uncoordinated or
even sloppy.


Meetings with end users can become time
consuming.


The final result could be completely different to
what was requested in the first place
.


Methods of prototyping


Piloting


Test the feasibility of the design
proposal


Modelling


building to develop an
understanding of the user’s requirements


Throw
-
away prototyping


Pilot and modelling
are throw away types


once they achieve their
purpose the real system is built.


Evolutionary prototyping


each prototype built
is a step closer to solution.