> I wrote about this -
https://www.ebiester.com/agile/2023/04/22/what-agile-alterna... - Royce was describing what he saw as an anti-pattern that it was risky and invited failure without iterations.
Yes, that's why his paper essentially said "you're going to have to build two." One to figure out the mistakes you can't predict ahead of time, and the second for the real deal. Do your best to get through the first one as fast as you can, but still deliberate enough that there won't be any bugs left behind for the second one.
But a third or subsequent iteration was definitely a failure in his mind, and even building two (or one-and-a-half, depending on your framing) was simply a concession to the reality that actual implementation would run into unpredictable issues, for much the same reason computer science had already learned the halting problem was undecidable.
I have a book with his paper and to the extent he speaks of iteration as desirable, it is only iteration between succeeding steps of the overall 'waterfall'. E.g. in an ideal world you iterate between system requirements and their decomposition into software requirements (updating the system reqs as necessary to ensure the software reqs you're writing are accounted for). Likewise for system requirements to software analysis, and so on.
As you point out, he mentions that this concept is “risky and invites failure”, and goes on to allow for re-refinement and re-implementation of the software requirements and program design phases based on experience from the testing phase. But he goes on to emphasize: “However, I believe the illustrated approach [waterfall with reimplementation post-test] to be fundamentally sound”.
The rest of his paper then goes into the detail of these phases, and he specifically notes early on that there is a natural question, of how much documentation is enough? And he gives a very clear answer: “My own view is ‘quite a lot’; certainly more than most programmers, analysts or program designers are willing to do if left to their own devices.”
It's not an accident that the DoD software acquisition requirements based on waterfall as mentioned by the other comments were so numerous or onerous. As Dr. Royce puts it:
- “The first rule of managing software development is ruthless enforcement of documentation requirements”
- When asked to review software projects the first thing he does is review the documentation. If the documentation is seriously lacking his recommendation is to replace the whole project management and shift 100% of work to fixing documentation.
- “Management of software is simply impossible without a very high degree of documentation”
- If procuring a $5M hardware device he'd expect a 30 page spec to suffice. If procuring a $5M software system, he'd “... estimate a 1,500 page specification is about right.”
I wasn't pulling "thousands of pages" from thin air. It's right in his paper and he's extremely clear about this. It's not an off-hand remark, he goes on to justify why he thinks that mass of documentation is required.
I want to emphasize that he's writing from the problems he was facing in his era. Computer systems necessarily were room-sized installations, interactive computer time was incredibly expensive, but paper was cheap. There was no Internet to speak of to share powerful and efficient open-source libraries. There was no "continuous deployment" or "continuous integration".
The system had to work well pretty quickly after the subsystems were built, installed, integrated and tested or this newfangled computer system that cost millions in 1960s dollars to run per month would be nothing more than a money sink while the nerds tried to troubleshoot.
Nowadays we don't develop under those kinds of strictures and we've put tremendous investments into allowing real useful systems to be developed using the simpler processes that even back then were much easier to develop around, when it could be used (Dr. Royce's paper even leads off by describing the 'nice' process as he explains why you can't use it as system size grows). The voluminous test documentation he's propose are things we pretty much do write today, but we call them test suites and we grow them along with the program, rather than write them all months before coding.
I think there's a lot to be said for what a modern-day waterfall process might look like with the technologies and iteration speeds available to us now, the only problem is that I think it will still resemble agile more than it would resemble the process Dr. Royce described.