1. SSA(D) vs OOAD
M. Pickard
CSC 513

2. Different Perspectives . . .
SSA (and design)
Data and actions considered separately.
Emphasis on data structures, procedures.
OOAD
Data and actions considered together.
Emphasis on classes, objects.

3. Steps in OOA
Use-case modeling
Class Modeling
Dynamic Modeling

4. OOD Create interaction diagrams
sequence diagrams, collaboration diagrams
Build a detailed class diagram, or object model
packages of classes
relationships owned by the package
hierarchy of packages
Design the product using objects
Proceed to detailed design

5. Structured Systems Analysis (SSA)
Analysis, resulting in Specifications
9 Step Approach (Gane and Sarsen)
Draw DFD
Define scope of product & operational approach
Refine/define data flows
Define logic of processes
Define data stores
Define physical resources
Determine I/O specifications
Perform sizing (volumes, frequencies)
Determine hardwire requirementss
Other variations

6. SSA - Specifications Semiformal techniques Data Flow Diagram (DFD)
Entity Relationship Diagram (ERD)
Decision (Logic) Table (DLT)
Decision Tree

7. SSA - Specifications Formal techniques Finite State Machines
Petri Nets Z
Formal specification language
pronounced “zed”
Other

8. Structured Methods - Design
Architectural design
Structure charts
Map DFDs to structure chart
Global data structures
Proceed to detailed design

9. SSA(D) vs OOAD
The differences become very apparent in the activities that take place after requirements gathering and before detailed design.
SSAD does not preclude use of OOPL.
OOAD does not preclude use of procedural language.

10. Architectural Design - Important Principles
Minimize coupling
Maximize cohesion
Use information hiding
Documentation
design decisions
design architecture

11. Detailed Design Identification of modules, i.e, program unit
purpose, preconditions, postconditions
Description of interfaces between program units
Module specifications
narrative or structured English
semiformal or formal methods to describe module functionality
DLT, FSM, other
linked closely to implementation environment
programming language, operating system, etc
definition of local data structures

12. Implementation
Using the detailed design, construction begins . . .