What is the V-Model?

Process model for IT development projects

The V-Model is a process model for IT development projects and registered as a trademark of the Federal Republic of Germany. The “V” visualizes a comparison of validation and verification in the course of a development. Thus it poses two important questions:

• Validation: Are we doing the right work?
• Verification: Are we doing the right work?

The special thing about the V-Model is that it looks at a development from a technical and functional point of view and defines quality assurance measures. Depending on the type of development, the V-Model comprises more or fewer phases. On the left side of the “V” you will find

• the requirements definition, which describes usage requirements or stakeholder requirements,
• the functional system design with the definition of system requirements, documented e.g. as Systems Requirements Specification,
• the technical system design with the system architecture as implementation of the system requirements
• and the component specification.

This is followed by programming or implementation at the foot of the “V”, which then leads to the right side of the “V”. There you will find

• the component test (as opposed to the component specification),
• the integration test (as opposed to the technical system design),
• the system test (compared to the functional system design)
• and the acceptance test or acceptance test (compared to the requirement definition).

The feedback loop in the V-Model

In the case of the V-Model, the test phases (right side of the “V”) are used to test against the specifications (left side of the “V”). Feedback between the individual phases is also possible in the V-Model, which was first described by Barry W. Boehm, a US software engineer, in the Guidelines for Verifying and Validating Software Requirements and Design Specifiations in 1979. In contrast to a waterfall model, however, it requires the specification of corresponding tests at an early stage – e.g. when defining the requirements or designing the architecture.

Notes:

In Germany, federal authorities are required to use the V-Modell in its current form – the V-Modell XT, Version 2.3 – as a process model. Alternatively, various alternatives such as V-Modell XT Bund, V-Modell XT Bayern or V-Modell XT Bw can be used. However, there are no valid and verified statistics on the use of these alternatives.

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