Policy and Details in Software Architect
Software systems can be decomposed into two major elements which are Policy and Details. The policy element embodies all the business rules and procedures. It is where the true value of the system lives.
The details are those things that are necessary to enable humans, other systems, and programmers to communicate with the policy, but that do not impact the behavior of the policy at all. They include IO devices, databases, web systems, servers, frameworks, communication protocols, and so forth.