Layering

Layering is one of the most common techniques that software designers use to break apart a complicated software system. It serves to help us in Separation of Concerns.

Advantages of Layering

• Reuse of Layers
• Standardization possibilities
• Dependencies are kept local
• Exchangeability
• Raise the level of Abstraction

Some of the Drawbacks

• Cascades of changing behavior (Ex: Adding a field to the database and its ripple effect in all the layers)
• Lower efficiency
• Layers lacks support for the easy recombination and reuse of components.

POSA Volume 1 and PoEAA are good places to read more stuff on this.

We’ll look into some of the popular schools of thought on layering.

POSA: Pattern Oriented Software Architecture

PoEAA: Patterns of Enterprise Application Architecture