Georgia State University
DFDs to Structure Charts
First Level Data Flow Diagram
0 Library System
1
Book Catalog
3 2
Borrowers List
Georgia State University
DFDs to Structure Charts
Functional Decomposition
0 Library System 1 2 3
2.1
2.2
Georgia State University
DFDs to Structure Charts
Structure Chart
Structure Chart Example Q: Where do the modules come from?
Logical Design
Executive Module 'Update File' Top because it calls all others none call it at this level
Module 1 e.g. Read
Module 2.. e.g. Update
Module n e.g. Write
Open FIle
Georgia State University DFDs to Structure Charts
Structure Chart
Structure Chart Example Q: Where do the modules come from?
Physical Design
2
Executive Module 'Update File' Top because it calls all others none call it at this level
1
3
Module n e.g. Write
Module 1 e.g. Read
Module 2.. e.g. Update
Open FIle
Georgia State University DFDs to Structure Charts
DFD to Structure Charts?
0 Library System
1
Book Catalog
?
Module 1 e.g. Read Open FIle
Structure Chart Example Q: Where do the modules come from?
3
2
Executive Module 'Update File' Top because it calls all others none call it at this level
Module 2.. e.g. Update
Module n e.g. Write
Borrowers List
Georgia State University
DFDs to Structure Charts
Why Divide Things Up?
Logical Design
– Simplifies understanding
“divide and conquer”
– Allows parallel development
Physical Design
– Separately compilable modules one change should not require a complete build
Georgia State University
DFDs to Structure Charts
Basic Design Goals
Fitness for purpose
– the system must work, and work correctly – it should perform all tasks as specified within the constraints of the resources
Robustness
– the design should be stable against changes to features such as file or data structures
Georgia State University
DFDs