The V-Model is Dead. Long Live the V-Model!

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Feature Owner and Chief Requirements Engineer

The V-model does not restrict a person from performing more than one role. Using small teams to flexibly fulfill all roles on the left side of the V-model to create a specification for a feature has been shown to increase commitment because the people enjoy taking responsibility for ensuring building something with which they can identify. The teams are responsible that customer requirements are fulfilled.

Development of requirements across the levels of the information model.

A lot of people associate a V-model with the Waterfall Model. A V-model is a static model that specifies roles, tasks, information, and relationships between information. The information may be produced in any order that makes sense to the authors.

Requirements from higher levels will guide the production of requirements at lower levels. Also requirements at lower levels guide production of requirements at higher levels as the possibility to satisfy higher level requirements is checked and compromises negotiated.

Requirements from higher levels set aims to be achieved. Requirements from lower levels document the constraints that design decisions and real-world situations introduce.

The Waterfall was first introduced in an article by Dr. Winston W. Royce in 1970 in his article entitled MANAGING THE DEVELOPMENT OF LARGE SOFTWARE SYSTEMS. Dr.Royce recommends an iterative incremental approach to software development. In building to this conclusion he built up a model from a uni-directional flow of tasks to a more complete and practical model. See Figure 4.

Dr. Royce used this to emphasise that this was not the recommended way to develop large software systems. Unfortunately over the years many have not read the paper but the diagram has entered legend, and some people have not taken the warning not to use the waterfall model. The waterfall model had the charm of being simple and memorable. Unfortunately the waterfall model did not have the charm of being very useful.

Agile

The basis for what today is called “Agile” is laid here by Dr. Royce. The iterative aspects will be very familiar to modern developers who know of the 12 principles behind the Agile Manifesto, with lessons learned from implementation being fed back directly into the development of requirements and the design process. The incremental aspects will be familiar to anyone, for instance, that has heard of Sprints from Scrum.

The V-model is an ideal static model to apply these iterative and incremental dynamic models to.

The V-model helps to organise the derivation of interfaces as larger challenges are divided into traceable, manageable, and achievable work packages.

The V-model also provides a plan for building components into sub-systems, and for combining sub-systems to create reliable working systems to fulfill the customer requirements.

Conclusion

The V-model represents graphically; ownership of and relationships between information.

The V-model is a static model and does not restrict sequence of creation of artefacts.

The V-model supports iterative creation of a feature or capability, and also the incremental introduction of features or capabilities to a system.

The V-model supports any number of levels, with a system being decomposed as many or as few times as is deemed useful.

The V-model is state-of-the-art.

Literaturverzeichnis

MANAGING THE DEVELOPMENT OF LARGE SOFTWARE SYSTEMS

Dr. Winston W.Royce

https://www.cs.umd.edu/class/spring2003/cmsc838p/Process/waterfall.pdf

Manifesto for Agile Software Development

http://agilemanifesto.org/

* Colin Hood hat seit 1977 die Evolution der Steuerungssysteme von relaisgestützten Systemen über programmierbare logische Controller (PLCs) bis hin zu modernen softwaregesteuerten Safety Critical Systemen begleitet.

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Software Process Models