Software Development Life Cycle(SDLC) Incremental Model

The incremental model is an intuitive approach to the waterfall model.  Multiple development cycles take place here, making the life cycle a “multi-waterfall” cycle.  Cycles are divided up into smaller, more easily managed iterations.  Each iteration passes through the requirements, design, implementation and testing phases.

A working version of software is produced during the first iteration, so you have working software early on during the software life cycle.  Subsequent iterations build on the initial software produced during the first iteration.

Incremental Life Cycle Model

Advantages

• Generates working software quickly and early during the software life cycle.
• More flexible – less costly to change scope and requirements.
• Easier to test and debug during a smaller iteration.
• Easier to manage risk because risky pieces are identified and handled during its iteration.
• Each iteration is an easily managed milestone.

Disadvantages

• Each phase of an iteration is rigid and do not overlap each other.
• Problems may arise pertaining to system architecture because not all requirements are gathered up front for the entire software life cycle.

Thanks
(Faisal Sikder)

 

Software Development Life Cycle(SDLC) Spiral Model

The spiral model is similar to the incremental model, with more emphases placed on risk analysis.  The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation.  A software project repeatedly passes through these phases in iterations (called Spirals in this model).  The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed.  Each subsequent spirals builds on the baseline spiral.

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 the risk analysis 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.

In the spiral model, the angular component represents progress, and the radius of the spiral represents cost.

Spiral model of SDLC

Advantages

• High amount of risk analysis
• Good for large and mission-critical projects.
• Software is produced early in the software life cycle.

Disadvantages

• Can be a costly model to use.
• Risk analysis requires highly specific expertise.
• Project’s success is highly dependent on the risk analysis phase.
• Doesn’t work well for smaller projects.

Thanks
(Faisal Sikder)

 

Software Development Life Cycle(SDLC) Waterfall Model

This is the most common and classic of life cycle models, also referred to as a linear-sequential life cycle model.  It is very simple to understand and use.  In a waterfall model, each phase must be completed in its entirety before the next phase can begin.  At the end of each phase, a review takes place to determine if the project is on the right path and whether or not to continue or discard the project.  Unlike what I mentioned in the general model, phases do not overlap in a waterfall model.

Waterfall model of SDLC

Advantages

• Simple and easy to use.
• Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process.
• Phases are processed and completed one at a time.
• Works well for smaller projects where requirements are very well understood.

Disadvantages

• Adjusting scope during the life cycle can kill a project
• No working software is produced until late during the life cycle.
• High amounts of risk and uncertainty.
• Poor model for complex and object-oriented projects.
• Poor model for long and ongoing projects.
• Poor model where requirements are at a moderate to high risk of changing.

Thanks
(Faisal Sikder)