A Goldratt technique came in handy to map out where I see the conflict between CCPM and EVM that I referred to in my last post. Please excuse it’s sloppiness, I will try to make a cleaner computer-generated version later on, but I think I may be refining this later on anyway.
I’ve never seen an evaporating cloud with more than 1 requirement for each of the prerequisites, but I found it necessary to have a requirement which stems from both CCPM and EVM. The conflict indicated between employing Critical Chain and EVM stems from different behaviors being driven by the two. Critical Chain supports behaviors that focus on efficiency with tasks on the Critical Chain , thus improving the outcome of the project. EVM supports behaviors that make it appear overall cost efficiencies are good, even if those efficiencies are being achieved on tasks that aren’t critical to the completion time of the project. Project managers might decide to work on some easier non-critical tasks if their EVM is going to fall short and get a short-term EVM win, but if that happens it throws EVM‘s predictive power regarding schedule out the window.
The resulting direction from this is to modify the budgeting and cost control tools in the Critical Chain body of knowledge. It needs to use buffer management methods for cost, to control the project that is implemented in such a way to make it compatible with existing EVM metrics. There would be a single project cost buffer which is already part of the CCBOK. Cost buffer management would be used for controlling project costs, in addition to an accurate EVM translation based on cost buffer utilization compared to planned utilization.
Note: from a cost perspective, all tasks are on the Cost Critical Chain (CCC) because cost over run in any task will make the project over budget unless other tasks have under runs. It makes no difference if they are on the schedule’s critical chain. That’s why there’s only 1 cost buffer, the project cost buffer.