Software Engineering

1
Software Engineering

• Software Design -- OO
• Lecture 10

2
Focus

• Abstraction
• Information Hiding
• Functional independence
• Modularity

3
The 4 models

• Subsystem Design
• Class and Object Design
• Message Design
• Responsibilities design

4
Differences with respect to structured design

• No hierarchical structure in architectural design

5
Issues

• Decomposability
• Composability
• Understandability
• Continuity
• Protection

6
Meyers Design principles

• Linguistic modular units
• Few interfaces
• Small interfaces
• Explicit interfaces
• Information hiding

7
OO Design approaches

• Each analysis has its own design
• Not as clear the end of OOA and the beginning of
  OOD
• OOA classes, OOD objects???
• UML
• system design
• object design

8
Subsystem design

• Partition analysis model into subsystems
• Identify concurrency
• Allocate subsystems to processors and tasks
• Develop a design for user interface
• Strategy to implement data management
• Identify global resources and control mechanisms
  to access them

9
Subsystem design

• Design control mechanism
• Consider boundary conditions
• Review

10
Object design

• Two parts
• Protocol description
• Implementation description

11
Class Design

• Initial classes
• Persistent classes
• Class visibility
• Operations and their visibility
• Methods
• Attributes
• Dependencies
• Associations

12
Object design

• Of algorithms and data structures
• Same as for structured

13
Message design

• Simply specifying each interface exactly.

14
Design Patterns

• For reuse
• Name
• Problem to which it is applied
• Characteristics
• Consequences of applying it
• Used in inheritance and composition