The Spiral Model is a software development lifecycle model that combines elements of prototyping and the waterfall model. It involves iterating through phases for communication, planning, modeling, construction and deployment in spirals to obtain early feedback from customers. Each iteration allows for refinement of deliverables based on customer evaluations and helps manage risks for large, expensive and complex projects.

1. Spiral Model
SOFTWARE DEVELOPMENT LIFE CYCLE (SDLC)
Bilal Bashir, Roll no: 09
Syed Shahzaib Sohail, Roll no: 19
Khuram Junaid, Roll no: 22

2. Antiquity
 Spiral Model was first described by "Barry Boehm"
in his 1986 paper "A Spiral Model of Software
Development and Enhancement".
 Boehm describes the spiral model as a "Process
Model Generator".
 Later in 1988, Boehm published a similar paper to
wider audience.

3. Spiral Model?
 Spiral model is a SDLC model used in
Information Technology.
 It combines the features of prototyping and
waterfall model.
 It is best suitable for complex, expensive and
large projects.

4. Spiral Model
 The Spiral Model
involves five phases.
 Each part of the project is
done through a spiral
(Iteration).

5. Spiral Model
Communication:
Tasks required to establish effective
communication between developer and customer.
Planning:
Tasks required to define resources, timelines and
other project related information.
Modeling:
Tasks required in building one or more
representations of the application.

6. Spiral Model
Construction and Release:
Tasks required to construct, test, install.
Deployment:
Tasks required to deliver the software, getting
feedbacks etc.

7. Spiral Model
 Based on a customer evaluation, the
development process enters into next iteration.
 Following the feedback suggested by the
customer.
 The process of iteration along the spiral
continues throughout the life of the software.

8. Advantages
 Provides early indication of risks, without much
cost.
 Users the systems early.
 Early and frequent feedback from users.
 Emphasize flexibility and extensibility.
 High quality product can be produced.

9. Disadvantages
 Time spent for evaluating risks too large for small or
low-risk projects.
 Time spent for planning, resetting objectives, doing risk
analysis and prototyping may be unnecessary.
 Risk assessment expertise required.
 Spiral may continue indefinitely.
 In fixed budget development, spiral model can be a
problem.

10. When To Use?
 When costs and risk evaluation is important.
 From medium to high risk projects.
 Long term project commitment.
 Users are unsure of their needs.