1. The Waterfall Model ----- A Case Study
SOFTWARE LIFE-CYCLES
The Waterfall Model
-----
A Case Study

2. Software process / Life-Cycle?
A project is a set of
activities, interactions and results ...
A “life-cycle” or a software process is the
organizational framework for a project.

3. The Waterfall Life-Cycle
is the ancestor of all other models
still prevalent in practical application
exists in many variations
supported by a multitude of tools
no at all a perfect solution

4. The WATERFALL MODEL Requirements System Design Detailed Design
Implementation
Installation & Testing
set of activities: sequential phases

5. The WATERFALL MODEL Requirements System Design Detailed Design
Implementation
Installation & Testing
transformation of results includes verification

6. The WATERFALL MODEL Requirements System Design Detailed Design
Implementation
Installation & Testing
completeness
of activities:
Maintenance

7. The WATERFALL LIFE-CYCLE: interactions Requirements System Design
Detailed Design
Implementation
Installation & Testing
Maintenance

8. Requirements : Maintenance
Cost Ratio of Errors
Requirements : Maintenance =
1 : 200

9. Activities during Phases
Requirements: establish your customer’s needs
System Design: develop the system’s structure
Detailed Design: develop module structures
Implementation: write source-code
Testing: check what you have developed
Installation: bring the system into production
Maintenance: correct, adapt, improve

10. Results of Phases Requirements: software requirements specification
System Design: software design chart; interfaces
Detailed Design: module specifications
Implementation: programs, files, etc...
Testing: test suits and test results
Installation: run-time version of the system
Maintenance: new version or release of the system
==> Documents

11. Discussion Questions What is Software Engineering?
Software Engineering vs. System engineering
What are the attributes of a good software?
What are the key challenges facing software engineering today?

12. Alternative Life-Cycles
Phases remain similar
Results remain similar
INTERACTION changes

13. End of Section 1a
coming up:
more about life-cycles ...