The V-Model framework is very common in product development to associate the documents between the product requirement document, the function requirement document, design specification, the test specification, etc. It is called the V-Model because these documents are connected in V shape. The V-Model has a good compatibility with QFD (Quality Function Deployment) so the V-Model and the QFD are used together in a DFSS project.
Both the V-Model and the QFD decompose the high-level requirements to the detailed requirements hierarchically in layers, however, there are two main differences between them. First, the requirement documents in the V-Model write all requirements sentences with texts. The QFD on other hands writes only the NUD (New, Unique, and Difficult) requirements. Second, the requirement documents in the V-Model don’t specifies the priorities of the sentences in general, but the QFD quantitatively specifies the priorities and the target values.
It is because almost 80% of the requirements for the new product development could be reuse of the existing product requirements, and the rest about 20% of the requirements could be the NUD requirements. So the requirement documents in the V-Model contain both the existing product requirements and the NUD requirements, and the QFD is used to decompose only the NUD requirements to integrate the decomposed NUD requirements to the requirement documents in the V-Model.
There are three advantages to use the QFD in the V-Model:
- The hierarchy of QFD matches with the V-Model, and the decomposed requirements can directly be integrated to the requirement documents in the V-Model
- The decomposed target values in the QFD can be used in the test specification
- The identified priorities in the QFD can be used for the prioritization in the project management (Schedule, budget allocation, resource allocation, etc.)
If there is a problem, it could be the document management. The more increases number of documents, the harder becomes the document maintenance. Using a document management software is effective for managing the many documents in the V-Model. I am using IBM Rational DOORS for the requirement document management. For the QFD, there are many commercial software (i.e., QFD editors).