The broken iron triangle
Businesses would like to know what are getting, for what price, and when they are getting it. This is the most common misconception that ruins quality in all our software projects.
The following diagram is the broken iron triangle:
The corners of the triangle represent the three targets you would like to lock down in order to have predictability. However, these are impossible to lock down if you want quality.
Locking down features means deciding on a set of features that should be delivered. This often comes from the client who wants to know what they are getting. The problem, as often shown in agile projects, is that they don't really know what they want before seeing results. Once there is a first demo version of an application, new ideas start popping up and the original scope is not valid anymore.
Locking down cost is done when the client requires a price tag on the system. Trying to estimate the work, a practice that is imprecise, most often requires this...
