Allow me to be a bit provocative: Level 5: your work doesn't exist until it has been formally proven to be correct. It's obvious that the amount of effort inv

Allow me to be a bit provocative: Level 5: your work doesn't exist until it has been formally proven to be correct. It's obvious that the amount of effort involved in this is so huge that it should only be considered in a select few problem domains. The same is true for the other levels. They're just a scale of increasing formalization/rigor, but you've said nothing to justify why they should be applied universally. I think it's important to keep in mind that these levels (or something analogous) exist, but different domains have different sweet spots and a deliberate choice needs to be made for each project.