Wigers, you're wrong! Once again about iterative and incremental development

Probably everyone who has ever tried to understand the specifics of various approaches to software development asked questions: what is the difference between iterative and incremental development? Agile - iterative? RUP - incremental?

Under the cut another discussion on this topic and an absentee dispute with Karl Wigers.

In the 3rd edition of Karl Wiigers' book “Developing Software Requirements” there is an illustration demonstrating the distribution of efforts to work with requirements throughout projects with different development life cycles (SDLC).

So, the picture separates Agile and iterative approaches. Is this correct?

First, let's define the terms.

• Iteration is the repetition of operations in order to process the results of the previous stage.
• Increment - an increment of the results of the previous stage.

Wikipedia tells you :

“Flexible development methodology (Agile software development, agile methods) - a series of approaches to software development focused on the use of iterative development ...”

This means that if, as part of a sprint in a flexible Scrum or an iteration in RUP, you process the results of the previous stage and at the same time implement new parts of the product, your development is iterative and incremental.

Below is an image explaining the difference between iterative and incremental development using the example of creating a portrait of Karl Wigers.

Conclusion It is
incorrect to separate flexible and iterative approaches. Wigers, you're wrong!