The trouble is, even the expert doesn't fully grasp the whole thing because when it comes to complex systems, the individual components of the process are interwoven with one another. The expert never has complete access to the necessary information. And the situation's complicated even further by the fact that experts are usually not aware of their own ignorance. The ignorance can take various forms. For instance, a lot of details of the system are invisible to managers. Some may be difficult to describe, learned on the job and well known by workers perhaps, but impossible to describe in a way that's helpful. And there are some things that people know or do that they're not even aware of. Now, let's consider two types of mistake that can occur when a manager actually starts to set up a duplicate system to replicate a successful process. Firstly, perhaps he forgets that he was just trying to copy another process, and starts trying to improve on it. Another mistake is trying to use the best parts of various different systems, in the hope of creating the perfect combination.