Monsters & Legends

This negative view, to what was once the de-facto approach to software development, is actually far closer to Royce’s original words on Waterfall than many seem to know…

The Truth & Technology

In Royce’s original paper, he shows a progression of activities, that came to be known as the waterfall model.

What we rarely hear of is Royce’s original words on the subject:

“…the implementation described above is risky and invites failure.”

Further to this, Royce goes on to explain that the reason that this cannot work is because there are too many things we cannot analyse up-front:

“The testing phase which occurs at the end of the development cycle is the first event for which timing, storage, input/output transfers, etc., are experienced as distinguished from analyzed. These phenomena are not precisely analyzable. They are not the solutions to the standard partial differential equations of mathematical physics for instance.”

He explains that we need feedback loops. He goes on to warn of (a conservative) 100% overrun in schedule and costs:

“…invariably a major redesign is required. A simple octal patch or redo of some isolated code will not fix these kinds of difficulties. The required design changes are likely to be so disruptive that the software requirements upon which the design is based and which provides the rationale for everything are violated. Either the requirements must be modified, or a substantial change in the design is required. In effect the development process has returned to the origin and one can expect up to a 100-percent overrun in schedule and/or costs.”

Some of Royce’s strategies, like “Involve the customer” and obtaining early feedback, have lived on in modern (Agile) methodologies. Beyond that, we should remember that his specific recommendations on how to solve the problems of a waterfall model were all based on the technology of the time.

Pot-Roast & The Cost of Change

In 1970, computing was much more expensive than it is today. In those days, changing software was far more expensive than changing pictures and words on paper. It was also much harder to express your design in a human-friendly way in the programming languages of that time. As a result of these and other factors, documentation was a major part of how Royce tried to solve the inherent problems of the Waterfall model.

Technology, tools & thinking have moved on and our documentation no longer needs to be static. It lives. It can breath. The specification can automatically verify that the implementation does what we said it should do (e.g. as in BDD Specs or ATDD/TDD Tests). Modern programming languages allow us to express the design and our understanding of the domain far more clearly, negating the need to first detail our thoughts on paper in natural language. We simply don’t have to cut the ends off that pot-roast anymore.

Only now, at the end…

Waterfall, thanks to the popularity of Agile, has gone from something I was shown at school as “how software is developed” to being seen in the light that it was originally presented – how software should not be implemented.

This is despite those who still profess the legitimacy of Waterfall and those still shocked and surprised when they hear of Royce’s own words against the monster he unintentionally created.

As for my name, I hold out little hope for change. I doubt that the world will use my name as it was originally intended and so I have resigned myself to needing two domain names… one with an ‘H’ in it, and the correct one without – I wonder which one brought you here.