Traditional software development models

Water fall model / Linear sequential model 
Water Fall Model
The waterfall Model illustrates the software development process in a linear sequential flow. This means that any phase in the development process begins only if the previous phase is complete.
  • This model is easy to understand easy to implement 
  • Is is suitable for small projects 
  • No changes in the middle of the project
Spiral Model
Spiral Model
The spiral model is a risk-driven software development process model. Based on the unique risk patterns of a given project, the spiral model guides a team to adopt elements of one or more process models, such as incremental, waterfall, or evolutionary prototyping.


  • The requirement are prioritized based on the business requirement 
  • Is is suitable for large and complex projects
V- model 
V- Model
The V-model is a type of SDLC model where process executes in a sequential manner in V-shape. It is also known as Verification and Validation model. It is also known as Verification and Validation model. The V-Model is an extension of the waterfall model and is based on the association of a testing phase for each corresponding development stage.


  • Start testing from beginning of the project 
  • Testing include both validation and verification
  • Defect found at early stages cost of fixing defect is less 
  • As testing is involve from beginning better understanding of requirement.
Validation is the process of establishing documentary evidence demonstrating that a procedure, process, or activity carried out in testing and then production maintains the desired level of compliance at all stages.
Example: Reviews, static Testing   

After coding is done the application is validate as per customer requirement.
Example: Unit , system testing.

Different level of testing in V-Model :
1. Requirement Reviews : A requirements review is a manual process that involves people from both client and contractor organisations. They check the requirements document for anomalies and omissions. ... Informal reviews simply involve contractors discussing requirements with as many system stakeholders as possible.
2. Design reviews : A design review is a milestone within a product development process whereby a design is evaluated against its requirements in order to verify the outcomes of previous activities and identify issues before committing to - and if need to be re-prioritise - further work.
3. Code Reviews  : Code review is a software quality assurance activity in which one or several people check a program mainly by viewing and reading parts of its source code, and they do so after implementation or as an interruption of implementation. At least one of the persons must not be the code's author.


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