Object-Oriented Analysis Design (6)

System Sequence Diagram

• System sequence diagram(SSD)
  - Shows the events that external actors generate, their order, and inter-system events, for one particular scenario of a use case in sequence diagram notation.
  - Depict system behavior in terms of what the system does
  - Used in order to generate system operations.

 

Layered Architecture

• UML Package Diagrams illustrate the logical architeucture.
  - Logical architecture : a large-scale organization of the software classes into packages, subsystems, and layers.
  - Can also be summarized as Views in a Software Architecture Document(AD)
• Typical layers in object-oriented systems:
  - User Interface layer
  - Application Logic and Domain Objects layer
  - Technical Services layer
  

Software Architecture

• A software architecture is the set of significant decisions about the organization of a software system,
  - the selection of the structurzl elements and their interfaces by which the system is composed, together with their behavior as specified in the collaborations among those elements,
  - the composition of these structural and behavioral elements into progressively larger subsystems,
  - and the architectural style that guides this organization - these elements and their interfaces, their collaborations, and their composition.

 

Connections Between SSDs, System Operations and Layers

• In a well-designed layered architecture,
  - The UI layer objects will forward the requests from the UI layer onto the domain layer for handling.
  - The messages sent from the UI layer to the domain layer will be the messages illlustrated on the SSDs.