Mark Richards

As an architect, you must always justify your architecture decisions, particularly when it comes to choosing a particular architecture pattern or approach

each of the layers in the architecture is marked as being closed. This is a very important concept in the layered architecture pattern. A closed layer means that as a request moves from layer to layer, it must go through the layer right below it to get to the next layer below that one

Leveraging the concept of open and closed layers helps define the relationship between architecture layers and request flows and also provides designers and developers with the necessary information to understand the various layer access restrictions within the architecture