Many of the systems in the world can be classified as chain systems. So knowing the characteristics of a chain system gives you one good approach to work with. I got this concept of the chain system from Good Strategy Bad Strategy: Learning from a Master of Strategy.
When you pull on a chain, it breaks at its weakest link. A chain system is a system like this, where the weakest link determines the strength of the whole. In other words, it is a system with no detour to make up for a problem when one part fails.
One example of a chain system is the supply chain. The process of moving raw materials and finally turning them into finished goods is connected from start to end. If any one step is delayed, the whole process is delayed, because no step can be skipped.
In a chain system, the weakest link shakes the performance of the whole. That is why improving the performance of a chain system requires good diagnosis. You have to work out where the bottleneck forms. If your judgment is sound, you can get a remarkable improvement with few resources. You can even solve the problem with a surgical strike.
On the other hand, a chain system with no particular bottleneck is hard to grow as a whole, because every element has to be upgraded a little at a time. That is why a chain system with no weak points is hard to build. Just as a hexagonal person, strong in every trait, is hard to find. Just as it is hard to find someone who has mastered intellect, virtue, and body all together. It is hard to become a The Complete Human.
Put the other way around, this can also work as a moat. It keeps competitors from easily copying the chain. For example, no matter how well other companies make smartphones, it is hard to catch up with Apple's iPhone. Apple has built a huge UX chain through the integration among Apple devices: not only the iPhone but also the iPad, Apple Watch, and MacBook. To beat this chain, you would have to raise the experience of use and the integration on every device to Apple's level. It isn't just the smartphone that matters.
Beyond these business insights, the chain system can also serve as an important mental model for productivity, because productivity itself is a chain system. To produce value in knowledge work, you need enough energy, you need to focus it where it is needed, and you need to process information appropriately. Just like the supply chain mentioned earlier. In that process, without energy, concentration, and a proper way to take in and process information, it is hard to produce anything of value.
Writing, video production, and coding each have their own chain system. So high productivity in coding does not mean higher productivity in writing or video production. Still, I wonder whether there might be a common chain. Perhaps writing is the common chain for the productivity of knowledge workers. After all, writing is planning ability.