Layered Architecture

Question 1

What is layering?

Answer 1

Layering is a common practice to separate and organise code units by their role/responsibilities in the system.

Question 2

How does a layered system is organized is broad strokes?

Answer 2

In a layered system, each layer:

• Depends on the layers beneath it;
• Is independent of the layers on top of it, having no knowledge of the layers using it.

Question 3

What are the advantages of the Layered Architecture?

Answer 3

• We only need to understand the layers beneath the one we are working on;
• Each layer is replaceable by an equivalent implementation, with no impact on the other layers;
• Layers are optimal candidates for standardisation;
• A layer can be used by several different higher-level layers.

Question 4

What are the disadvantages of the Layered Architecture?

Answer 4

• Layers can not encapsulate everything (a field that is added to the UI, most likely also needs to be added to the DB);
• Extra layers can harm performance, especially if in different tiers.

Question 5

What is the Lasagna Architecture?

Answer 5

Lasagna Architecture is the name commonly used to refer to the anti-pattern for Layered Architecture

Question 6

What’s the difference between tier and layer?

Answer 6

Tier is a physical unit, where the code / process runs. E.g.: client, application server, database server;

Layer is a logical unit, how to organize the code. E.g.: presentation (view), controller, models, repository, data access.