The Human Factor in Software Engineering

I have just been correcting my students' homework about theory of constraints TOC. They had learned the network planning and critical path analysis CPA first, and now I see that I should explain the differences explicitly. This will lead to a philosophical excursion, but I am sure they will be able to follow.
TOC and CPA can be used for analyzing the same work processes, but their objectives are different:

• CPA optimizes the processe's duration. This is relevant when you produce something specifically for one customer and the duration between contracting and delivery are important. This can be a software project, but also producing an individually configured car.
• TOC optimizes the throughput. This is relevant when you produce a large number of identical products. In our exercise, we produce musical boxes. When we produce 5 music boxes per hour, we can sell this number. The customer does not mind how long the process takes. Therefore, parallelization of production steps is not as interesting as in CPA, because parallelization only saves calendar time, but not work time/ cost. Parallelization can even create cost in software engineering, e.g. when we start testing before the code is complete. We risk that code already tested is changed and must be retestet.

All together, we can summarize: Depending on which of the four corners of project manager's square (time, budget, scope or quality), you will use another method for analyzing the process, come to different results and take different measures.
For optimizing quality, of course, TOC and CPA are not made. Measuring and optimizing quality is another interesting topic but can be summarized by a simple "use standards".