Software Life Cycle Models

Software lifecycle models define the series of steps through which the product / project progresses. The models specify the various phases of the process and the order in which they are carried out.

The models provide guidance for project management ( eg. Major tasks to be tackled, milestones , progress etc.)

Different Software Life Cycle Models

1.Waterfall

2.V-shaped

3.Rapid Prototyping

4.Incremental

5.Spiral

1.Waterfall

• Consists of a set of phases that a project progresses through in a sequential order.
• Each phase must be completed before the project can progress to the next phase.
• At the end of each phase is some form of gateway, usually a formal review where that decision is made.
• There is no overlap between phases.
• Straight forward, simple to understand and use.
• Deliverables are frozen at the end of each phase and serve as the baseline for the following phases.
• The Userdoes not see the software until the end of the project (big bang software development).
• Changes are not supposed to happen or are limited or are tightly controlled.

Waterfall Model

2. V-Shaped Model

• Similar to waterfall except it emphasizes the importance of considering the testing activities up front instead of later in the life cycle.
• Each test phase is considered in its matching development phase:
• Requirements == System/Functional Testing
• High-Level Design == Integration Testing
• Detailed Design == Unit Testing

3.Rapid Prototyping

• Used to develop a quick implementation of the software prior to or during the software requirements phase.
•  The customer uses the prototype and provides feedback to the software developers as to its strengths and weaknesses.
• This feedback is used to refine or change the prototype to meet the real needs of the customer.
• Can either be evolutionary or throw away.
• Minimal time investment in prototypes.
• The system is then designed, constructed, and implemented using waterfall model
• Rapid prototyping has been enabled by the availability of modern programming tools

4.Incrememtal

• Allows a project to construct the software in incremental stages where each stage adds additional functionality.
• Each stage consists of design, code and unit test, integration test and delivery.
• Allows you to put functional software into the hands of the customer much earlier than either the waterfall or v-shaped model.
• You can plan the stages in such a way that you determine what functionality you do first. i.e., you may choose to deliver the most important functionality to the customer first.
• Provides tangible measures of progress.
• Requires careful planning at both the project management level and the technical level.

5.Spiral

• Developed by Barry Boehm.
• A risk-oriented software life cycle.
• Each spiral addresses major risks that have been identified.
• After all the risks have been addressed, the spiral model terminates as a waterfall software life cycle.
• Very much an iterative approach.
• You start small, explore the risks, develop a plan to deal with the risks, and then commit to an approach for the next iteration.
• Each iteration involves six steps:
• Determine objectives, alternatives, and constraints.
• Identify and resolve risks.
• Evaluate alternatives.
• Develop deliverables and verify that they are correct.
• Plan the next iteration.
• Commit to an approach for the next iteration.

• Mainly used for large projects

Software life cycles to be used at Sai Softek Services Pvt. Ltd., Pune

• Rapid Prototyping for external projects
• Incremental for in-house projects / products