Spiral Model.pdf

Spiral model

1. Spiral Model

2. The exact number of loops of the spiral is not fixed
and can vary from project to project.
Each loop of the spiral is called a phase of the
software process.
The exact number of phases through which the
product is developed can be varied by the project
manager depending upon the project risks.
A prominent feature of the spiral model is handling
unforeseen risks that can show up much after the
project has started.

3. Risk handling in spiral model
A risk is essentially any adverse circumstance that
might hamper the successful completion of a software
project.
As an example, consider a project for which a risk can
be that data access from a remote database might be
too slow to be acceptable by the customer.
Caching scheme / Faster communication scheme.

4. 1 Phases of the Spiral Model
Each phase in this model is split into four sectors (or
quadrants) as shown in Figure 2.12.
Quadrant 1: The objectives are investigated,
elaborated, and analysed.
Quadrant 2: The alternative solutions are
evaluated to select the best possible solution.
To be able to do this, the solutions are evaluated by
developing an appropriate prototype.

5. Quadrant 3: Developing and verifying the next level
of the software.
Quadrant 4: Reviewing the results of the stages
traversed so far.

6. Advantages/pros and disadvantages/cons
of the spiral model
Disadvantages:
1. For developers – complex model to follow
2. Counterproductive to use.
3. Not very suitable for use in the development of
outsourced projects.
Advantages:
1. Much more powerful than the prototyping model.

8. Spiral model as a meta model
The spiral model incorporates the systematic step-wise
approach of the waterfall model.
The spiral model uses the approach of the prototyping
model.


9. A COMPARISON OF DIFFERENT LIFE CYCLE
MODELS
The classical waterfall model can be considered as the
basic model and all other life cycle models as
embellishments of this model.
Iterative waterfall – feedback paths. / widely used /
only for well-understood problems. not suitable for
development of very large projects.
The prototyping model user requirements or the
underlying technical aspects are not well understood.
All the risks can be identified before the project starts.
User interface part of projects.

10. The evolutionary large problems which can be
decomposed into a set of modules for incremental
development and delivery.
object-oriented development projects
The spiral model is considered a meta model and
encompasses all other life cycle models.

11. Selecting an Appropriate Life Cycle
Model for a Project
1. Characteristics of the software to be developed:
For small services projects, the agile model is favoured.
For product and embedded software development,
the iterative waterfall model can be preferred.
An evolutionary model is a suitable model for object-
oriented development projects.
2. Characteristics of the development team:
3. Characteristics of the customer: