TechRepublic has an interesting article about the famous ‘three levers’, also known as the iron triangle: Cost, Time and Quality – you can have two of these but never all three. The article claims that once the project has started, ‘cost’ cannot be changed – which I’d have to agree with.
It’s interesting in that, for me, it’s a reminder of the importance of high quality requirements. This article essentially puts the emphasis on a clear scope definition, tied back to business rules. If you get your scope right, and agreed upon, then you’ll stand a much better chance of success – nothing radical here I suppose.
What’s makes this more complicated though, is if you think about this from an Agile perspective. The approach I’ve seen in the past when scope or features are increasing, is the project manager or account manager will say ‘no worries, I’ll ask the client for more money’. 9 out of 10 times it didn’t work, and we were left in an awkward situation. But according to standard agile approaches, this free-wheeling scope definition is a core part of the agile manifesto.
In my experience, the client would be quite happy with a precisely defined scope, and the project team would be more than happy to deliver within that. The key is to get it identified clearly enough, with the impacts documented. Hence, requirements being the key. You can still use Agile as a methodology, but I would recommend using formal change requests to accommodate changes, rather than ad-hoc adjustments.