1. Prepared by Syed Attique Shah BS (IT)6th Jahangir Azeem BS(IT)6th Software Lifecycle Models

2. Software Lifecycle Models Software System Passes through the following Phases, Vision - focus on Why Definition - focus on What Development -focus on How Maintenance -focus on Change

3. Software Lifecycle Models A Lifecycle Model is a series of steps through which the product progresses. Software Lifecycle Model depict the way you organize your activities. There are number of Software Development Lifecycle Models, each have its own Strengths and Weaknesses and suitable in different situation and project types.

4. Software Lifecycle Models The list of Models include the following, Build and Fix Model Waterfall Model Incremental Model Rapid Prototyping Model Spiral Model Object Oriented Models

5. Build and Fix Model It is unfortunate that many products are developed using what is called Build and Fix Model. In this Model the product is constructed without specification or any attempt at design. The developers simply build a product that is reworked as many times as necessary to satisfy the client. This model may work fro small projects but is totally unsatisfactory for big projects.

6. Waterfall Model Requirement Definition Software Design Implementation Integration Operation and Maintenance

7. Waterfall Model The first published model of software development process. Because of the cascade from one phase to another, this model is know as water fall model. It suggests a systematic and sequential approach to software development that begins at the system level and progress through the analysis, design, coding, testing and maintenance.

9. Difficult to establish all requirements explicitly, no room for uncertainty

10. Customer must have patience, not fast enough for delivery of modern internet based software difficult to trace requirements from analysis model to code

11. Inflexible partitioning of the project into distinct stages

12. This makes it difficult to respond to changing customer requirements

14. Rapid Prototyping

15. Incremental Model In the incremental Model the product is partitioned into smaller pieces which are then built and delivered to clients in increments at regular intervals. Since each piece is smaller and than the whole, it can be built and sent to the client quickly. This results in quick feedback for the client and any requirement related errors or changes can be incorporated at much lesser cost.

16. Incremental Model Requirement Definition (verified) Specification Phase (verified) Design For each build: Perform detail design, implementation and integration. Deliver to client Operation and Maintenance

17. Incremental Model Customer value can be delivered with each increment so system functionality is available earlier Early increments act as a prototype to help elicit requirements for later increments Lower risk of overall project failure The highest priority system services tend to receive the most testing

18. Spiral Model The main idea of this model is to avert risk as there is always an element of risk in development of software. In its simplified form a spiral model is waterfall model plus risk analysis. Each stage is preceded by identification of alternatives and risk analysis and is then followed by evaluation and planning for the next phase.

19. Spiral Model

20. Object Oriented Model Object Oriented model appreciate the need for iteration within and between the phases. There are number of these models. All of these models incorporate some form of iteration, parallelism and incremental development.

21. Questions Any One?