Iterative and Incremental Software Development: A Comprehensive Guide, Exams of Computer Science

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CS-

Software Engineering-

(SE-1)

Lecture: 03

Sequence [ Todays Agenda ]

Content of Lecture

• Iterative and Incremental Development
• Prototyping
• V-Model
• Spiral Model
• Rational Unified Process
• Rapid Application Development
• Introduction to Agile Development
• Introduction to Scrum and XP

Iterative and Incremental Model

The Incremental Model

Advantages of incremental model

1. Major advantage : it can result in better testing since testing

each increment is likely to be easier than testing the entire

system.

2. Similar to prototype each increment provides feed back

which is useful for determining further/final requirements of

the system.

3. Model proceeds in steps starting from the simple and key

aspects of the system.

4. A project control list is prepared that contains, in order, all

the tasks to be implemented in the final system; provides a

better control and progress monitoring of development.

The system grows incrementally (a little more is added each time) over time, iteration by iteration, and thus this approach is also known as iterative and incremental development There is neither a rush to code, nor a long drawn-out design step that attempts to perfect all details of the design before programming Work proceeds through a series of structured build- feedback-adapt cycles The result of each iteration is an executable but incomplete system; it is not ready to deliver into production Iterative and Incremental Development

Short is good!

Date slippage is illegal

If it seems that it will be difficult to meet the deadline, the recommended response is to remove tasks or requirements from the iteration, and include them in a future iteration, rather than slip the completion date Iteration Time-boxing (contd…)

Incremental development problems

• (^) The process is not visible.
  • (^) – Managers need regular deliverables to measure progress. If systems are developed quickly, it is not cost-effective to produce documents that reflect every version of the system.
• (^) System structure tends to degrade as new increments are

added.

• (^) – Unless time and money is spent on refactoring to improve the software, regular change tends to corrupt its structure. Incorporating further software changes becomes increasingly difficult and costly.

Incremental development and delivery

- Incremental development - (^) – Develop the system in increments and evaluate each increment before proceeding to the development of the next increment; - (^) – Normal approach used in agile methods; - (^) – Evaluation done by user/customer proxy.

• • Incremental delivery
  • (^) – Deploy an increment for use by end-users;
  • (^) – More realistic evaluation about practical use of software;
  • (^) – Difficult to implement for replacement systems as increments have less functionality than the system being replaced.

Software Prototyping Model

• (^) A prototype is an initial version of a system used to demonstrate concepts and try out design options.
• (^) A prototype can be used in:
  • The requirements engineering process to help with

requirements elicitation and validation;

• In design processes to explore options and develop a UI

design ;

• In the testing process to run back-to-back tests.

Benefits of prototyping

• (^) Improved system usability.
• A closer match to users’ real needs.
• (^) Improved design quality.
• (^) Improved maintainability.
• (^) Reduced development effort.