When partitioning a complicated software system, layering is one of the most common techniques. In a layered architecture, the software application is divided into various horizontal layers, with each layer located on top of a lower layer. Each layer is dependent on one or more layers below it (depending on whether the layers are open or closed), but is independent of the layers above it.
Layered architecture
Open versus closed layers
Layered architectures can have layers that are designed to be open or closed. With a closed layer, requests that are flowing down the stack from the layer above must go through it and cannot bypass it. For example, in a three-layer architecture with presentation, business, and data layers, if...
