Software Engg. process models

Submitted By:- Tauseef Ahmad
M.Tech(Software Engg.)
Aligarh Muslim University(India)

Outlines…
 Objective
 Software Process Models
 Five Models
 Advantages and Disadvantages of five models
 Conclusion and Future Work

2

Objective
 Represents five of the development models namely
waterfall, Iteration, V-shaped, spiral and Extreme
programming.
 Main objective, to represent different models of
software development and make a comparison
between them to show the features and defects of each
model

3

Software Process Models
 It is an abstract representation of a software process.
 It presents a description of a process from some
particular perspective as:
1. Specification – what the system should do and its
development constraints
2. Design– Production of software systems
3. Validation-- Checking the software to make sure it
is what the customer wants
4. Evolution– Changing the software in response to
changing demand

4

General Software Process Models
 Waterfall model
 Prototype model
 Rapid application development model (RAD)
 Evolutionary development
 Incremental model
 Iterative model
 Spiral model
 Component-based software engineering

5

Five Models
 This presentation will view the following five models
1. Waterfall model
2. Iteration model
3. V-shaped model
4. Spiral model
5. Extreme model
 These models are chosen because their features
correspond to most software development programs

6

1. Waterfall model
 It is the classical model of software engineering
 This model emphasizes planning in early stages, it
ensures design flaws before they develop
 consists of several non-overlapping stages
 Begins with establishing system requirements and
software requirements and continues with
architectural design, detailed
design, coding, testing, and maintenance
 serves as a baseline for many other lifecycle models

7

 following list details the steps for using the waterfall
model:

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 At the end of each stage, a review to determine
whether the project can proceed to the next stage is
held
Disadvantages
 The requirements must be stated before beginning the
design.
 There is no overlap between stages
 The waterfall method does not prohibit returning to
an earlier phase, this involves costly rework
 Because the actual development comes late in the
process, one does not see results for a long time
 Not suitable for projects of long duration because in
long running projects requirements are likely to
change. 9

Advantages
1. Easy to understand and implement.
2. Widely used and known (in theory!).
3. Reinforces good habits: define-before- design,
design-before-code.
4.Works well for projects where requirements are well
understood.
5.Clearly defined stages.
6. Easy to manage. Each phase has specific deliverable
and a review.

10

2. Iterative Development
 The project is divided into small parts
 allows the development team to demonstrate results
earlier on in the process and obtain valuable feedback
from system users
 each iteration is actually a mini-Waterfall process with
the feedback from one phase providing vital
information for the design of the next phase

11

Advantages
 Results are obtained early and periodically
 Progress can be measured
 Less costly to change the scope/requirements.
 With every increment operational product is
delivered.
 Testing and debugging during smaller iteration is easy
Disadvantages
 More resources may be required
 More management attention is required.
 Defining increments may require definition of the
complete system.
 Each phase of an iteration is rigid with no overlaps.

13

3. V-Shaped Model

Quality is guaranteed at each project stage.
14

 V-Shaped life cycle is a sequential path of execution of
processes
 Each phase must be completed before the next phase
begins.
 Testing is emphasized in this model more than the
waterfall model
 Testing procedures are developed early in the life cycle
Advantages
1. Simple and easy to use.
2. Each phase has specific deliverables.
3. Higher chance of success over the waterfall model due to
the early development of test plans during the life cycle.
4. Works well for small projects where requirements are
easily understood.

15

Disadvantages
1.Very rigid like the waterfall model.
2. Little flexibility and adjusting scope is difficult and
expensive.
3. Software is developed during the implementation
phase, so no early prototypes of the software are
produced.
4. This Model does not provide a clear path for problems
found during testing phases

16

4. Spiral Model
 Similar to the incremental model with more emphases
placed on risk
 It has four phases: Planning, Risk Analysis , Engineering
and Evaluation
 Requirements are gathered during the planning phase
 In the risk analysis phase, a process is undertaken to
identify risk and alternate solutions, A prototype is
produced at the end of this phase.
 Software is produced in the engineering phase along with
testing at the end of the phase.
 The evaluation phase allows the customer to evaluate the
output of the project to date before the project continues to
the next spiral.
 angular component represents progress, and the radius of
the spiral represents cost.
17

Spiral model Sector
1. Objective Setting 2.Risk Assessment and Reduction
3. Development and Validation 4. Planning
Advantages
1. High amount of risk analysis.
2. Good for large and mission-critical projects.
3. Software is produced early in the software life cycle.
Disadvantages
1. Can be a costly model to use.
2. Risk analysis requires highly specific expertise.
3. Project’s success is highly dependent on the risk
analysis phase.
4. Doesn’t work well for smaller projects .

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5. Extreme Programming
 Based on the development and delivery of very small
increments of functionality
 Agile method of development.
 Constant code improvement, user involvement in the
development team and pair wise programming
 Extreme Programming Practices
1. Incremental planning
2. Small Releases
3. Simple Design
4. Test first development
5. Refactoring
6. Pair Programming
7. Collective Ownership
8. Continuous Integration
9. On-site Customer 20

 Advantages
 Lightweight methods suit small-medium size projects
 Produces good team cohesion
 Emphasizes final product
 Iterative
 Test based approach to requirements and quality assurance
 Disadvantages
 Difficult to scale up to large projects where
documentation is essential
 Needs experience and skill if not to degenerate into
code-and-fix.
 Programming pairs is costly.
 Test case construction is a difficult and specialized skill
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Conclusion and Future Work
 it is concluded that
1.There are many existing models for developing systems
for different sizes of projects and requirements
2.Waterfall model and spiral model are used commonly
in developing systems
3. Each model has advantages and disadvantages for the
development of systems , so each model tries to
eliminate the disadvantages of the previous model
 for future works:
Suggesting a model to simulate advantages that are
found in different models to software process
management
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Software Engg. process models

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