The document discusses evolutionary development and incremental models for software engineering. Evolutionary development involves exploratory development where the initial system outline evolves over time based on customer feedback and new proposed features. The incremental model divides the software into separate modules that each go through requirements, design, implementation, and maintenance in iterations, delivering an initial version and accepting new requirements. Benefits include receiving early customer feedback, flexibility, and lowering overall project risk, while proper integration and design planning is needed.

1. Software Engineering, Slide 1
Objectives
 Evolutionary development
 Class Activity

2. Software Engineering, Slide 2
Evolutionary development
 Exploratory development
• Objective is to work with customers and to evolve a final system
from an initial outline specification. Should start with well-
understood requirements and add new features as proposed by the
customer.

3. Software Engineering, Slide 3
Requirements Collection for Evolutionary Model

4. Software Engineering, Slide 4
When we need It?
 Software Development is completed over a period.
 Business and product requirements often change as development
proceeds, making a straight line path to an end product unrealistic.
 When costume need the Initial version very fast.
 Each version of the Software called prototype.

5. Software Engineering, Slide 5
Evolutionary development

6. Software Engineering, Slide 6
Evolutionary development
 Problems
• Lack of process visibility;
• Systems are often poorly structured;
• Special skills (e.g. in languages for rapid prototyping) may be required.
 Applicability
• For small or medium-size interactive systems;
• For parts of large systems (e.g. the user interface);
• For short-lifetime systems.

7. Software Engineering, Slide 7
Incremental model
 According to incremental model, the software is divided into separate
modules(components).
 Each of these models have a separate set of activities.
 Including requirements gathering and analysis, design, implementation,
deployment and maintenance.
 When any components is ready, then the initial version of the software is
delivered to the customer.
 Start the new requirements for the new version.

8. Software Engineering, Slide 8
Example of the Incremental Model

9. Software Engineering, Slide 9
Incremental delivery
 Rather than deliver the system as a single delivery, the
development and delivery is broken down into increments with
each increment delivering part of the required functionality.
 User requirements are prioritised and the highest priority
requirements are included in early increments.
 Once the development of an increment is started, the requirements
are frozen though requirements for later increments can continue
to evolve.

10. Software Engineering, Slide 10
Incremental development

11. Software Engineering, Slide 11
Incremental development advantages
 Customer feedback is received after the delivery of each component.
 More flexible
 Early increments act as a prototype to help elicit requirements for later
increments.
 Lower risk of overall project failure.
 Easy to test and debug.
 Give quick results.

12. Software Engineering, Slide 12
Disadvantage
 Need a proper plan to integrate the components.
 Needs a proper design to integrate the components.
 More expensive as compared to the waterfall model.

13. Software Engineering, Slide 13
Key points
 Software processes are the activities involved in producing and
evolving a software system.
 Software process models are abstract representations of these
processes.
 General activities are specification, design and implementation,
validation and evolution.
 Generic process models describe the organisation of software
processes. Examples include the waterfall model, evolutionary
development and component-based software engineering.
 Iterative process models describe the software process as a cycle of
activities.