That’s a deeply asymmetric relationship, and it is one that we desire to have in our own systems. We want certain modules to be immune to others. For example, we don’t want the business rules to break when someone changes the format of a web page, or changes the schema of the database. We don’t want changes in one part of the system to cause other unrelated parts of the system to break. We don’t want our systems to exhibit that kind of fragility.
