1. BTS430 Systems Analysis and Design using UML
3- tier architecture in
Object-Level sequence diagrams

2. Three Tier Architecture
Presentation Layer (UI classes)
Business Logic Layer (data classes holding business logic)
Persistent Data Layer (databases, DBMS, data access classes)

3. Three Tier Architecture
Presentation Layer (UI classes)
Business Logic Layer (data classes holding business logic)
Persistent Data Layer (databases, DBMS, data access classes)

4. Three Tier Architecture
Presentation Layer (UI classes)
controller
Business Logic Layer (data classes holding business logic)
façade
Persistent Data Layer (databases, DBMS, data access classes)

5. Controller/Façade Controller Façade
Logic control for a component of a system
Does not “do” much; passes messages to the appropriate objects
Façade
A specialized controller
Acts as an interface into a subsystem (simplifies interaction with the subsystem)

6. Controller/Façade Controller Façade
In BTS430 we will use a controller for all interaction between the UI and the business logic
One controller per USE CASE
Typically named handler or controller e.g.
ManageCustomerHandler OR ManageCustomerController
Façade
In BTS430 we will use a façade as an entry point into the persistent data layer from the business layer

7. Controller/Façade
Protects logic layer from variations in the presentation layer and the data layer
UI, DBMS, DB changes, and so on
Promotes “cohesion” within each layer
Promotes “low coupling” between layers
Promotes reuse
Directs messages to the appropriate objects

8. Three Tier ArchitectureUI
Business Logic
Persistent Data