V model
The principle of the V-shaped model is in many ways similar to the cascade model. Most often it is used in systems where uninterrupted operation is extremely important. This is software for maintaining the life support of patients in medical institutions, emergency blocking systems and similar software.
A characteristic feature of this model is that it focuses on testing software that is in the early stages of development, including design. Testing happens in parallel with the development process - for example, unit tests are performed while writing code.
When should the V-model be used?
- If a software product needs rigorous testing, then the principles of the V-model (validation and verification) are most justified in this situation.
- For small and medium projects, with clearly defined requirements.
- In the presence of a large number of qualified testers.
Incremental model
The peculiarity of the incremental model is that in it the requirements for the software depend on the specific assembly. Because a product is being built in phases, its development goes through multiple iterations. This whole life cycle can be called a “multi-waterfall”.
The build cycle is divided into small and simple modules. Each one goes through rigorous requirements, design, coding, implementation, and testing.
The development process according to the incremental model begins with the release of a basic version of the product with minimal functionality. Then there is a “growth” of functions, which are called “increments”. The workflow continues until all previously planned functions are integrated into the system.
Iterative model
An iterative model, which is also called an iterative model, does not need to have a complete requirements specification at the initial stage. Development starts with the creation of certain functionality, which then becomes the basis for adding new functions.
The process of creating functions “in parts” is repeated over and over again, until it is completed according to the approved plan. Work continues until a working version of the product is received.
In the diagram attached here, you can see the iterative “development” of the Mona Lisa portrait. In the first iteration you see only a sketch of a portrait of a girl, in the second iteration you can already see the colors, the third iteration becomes more detailed and saturated. Process completed.
If we recall the incremental model, then the portrait will be written on it in a completely different way - piece by piece, from separate parts.
An example of the development of an iterative model can be voice recognition. Scientific research on this topic began a long time ago, first in the form of ideas, then practical implementation began. Each new iteration improved the quality of voice recognition. However, even now recognition cannot be called perfect. So the task is not yet completed.
When is the best time to use the iterative model?
- If the requirements for the system are clearly defined and understandable to everyone.
- The project is very large in scope.
- The main goal is defined, but implementation details may change in the course of work.
Spiral model
The “Spiral Model” is similar to the incremental model, but has a feature in the form of risk analysis. It is usually used for mission-critical processes where failure is simply unacceptable.
The spiral model includes four stages of work:
- planning;
- risk analysis;
- work on software design;
- checking the result and moving to a new stage.