Component Architecture: Layers, Objects, and Associations

Component Architecture

A component diagram illustrates the three layers:

• User layer (interface)
• Login layer (business rules)
• Data layer (database)

The use of interfaces and menus indicates who created the interface design.

Object Fundamentals

Class -> identity + state + behavior

Denormalization: The process of reverting from normalization, accepting redundancy and data dependencies to improve data performance. Data - Entity (instance, records)

Object Properties

Object properties:

• Encapsulation: Objects hide their attributes, state, and behavior from other objects.
• Inheritance: An object can inherit attributes and behavior from other objects.
• Overriding: The ability to change or modify inherited attributes or behavior.
• Composition: An object can be composed of other objects, where actions on the whole affect the parts (propagation).
• Polymorphism: An object or different objects respond or operate differently to a single message.

Associations and Messages

A condition-based procedure is executed when a specific condition is met.

An association enables message passing between two associated classes.

When associating two subjects or classes, the association can be:

• Bi-directional: Objects of both classes can send messages (more complex).
• Uni-directional: Only objects of one class can send messages to the objects of the associated class (preferred).

Association Class

Association class: Only used when a many-to-many relationship generates a single instance.

Message: The invocation of an operation from an object of one class to an object of another class within an association.

Message Types

• Message type:
• Synchronous: Sender waits for a response.
• Asynchronous: Sender does not wait for the receiver's response.
• Receiver-response: Sender does not wait for the receiver's response.
• Timeout: Receiver has a time limit to respond to the sender.
• Emitter controls messages based on the receiver's response.

Propagation Property

• Composition: What happens to the whole also happens to its parts, when the parts are contained within the whole.