1. Structured Design Tools
Dr. Merle P. Martin
CSU Sacramento

2. Agenda Design approaches Structured approach Hierarchical Chart
Data Flow Diagram

3. Design Approaches Traditional (bottom-up) Structured (top-down)
Radical Top-down
Prototyping

4. Traditional Design Approach
Bottom-up
Narrative, technical specs
User had to read them
Merely signed off
Resulting system
not expected by user
flaws

5. Structured Design Approach
Top-down
First derived at general level
Successive refinement of detail
Primitive level (coding)
Computer Assisted System Engineering (CASE)

6. Radical Top-down Approach
Used in this course
and in MIS 108, 119
Partial system development
stubbing out of primitive level modules
prioritization of modules
top priority modules developed first
Lends itself to Prototyping

7. Structured Approach Advantages
Reduces complexity (modularity)
Focuses on ideal (logical) system
Standardizes (team design)
Provides a future orientation
e.g.., future file
Relies less on artistry
engineering approach

8. Structured Approach Sequence
Hierarchical Chart
Physical DFD current system (WHAT/HOW)
Logical DFD current system (WHAT only)
Logical DFD proposed system (revised WHAT)
Physical DFD proposed system (revised WHAT/HOW)

9. Structured Approach Sequence
Figure 6.1-1, pg.. 184)

10. Hierarchical Chart Terms: parent,child,sibling functional primitive
control module
How long should chart be?

11. Hierarchical Chart - Colonial Heights
Figure 6-6, pg.. 164

12. Data Flow Diagram (DFD)
Purpose: communication with user
Components:
external entities (sources, sinks)
processes (subprograms)
data stores (files)
data flows (forms)
Symbols - Figure 6-7, pg.166

13. Data Flow Diagram (DFD)
Figure 6-9, pg Hierarchical Chart
Figure 6-10, pg Context Level Diagram
Figure 6-11, pg First Level Explosion

14. What You Should Remember
Different design approaches
Why Radical Top-down approach?
Structured Design sequence
Hierarchical Chart
DFD components and levels
Study Megavideo case (Case 6.1)