1. SOFTWARE LIFE-CYCLES
Beyond the Waterfall

2. The WATERFALL LIFE-CYCLE Milestones Requirements System Design
Standards
Detailed Design
Implementation
Installation & Testing
Documents
Maintenance

3. Problems with the Waterfall Model
sequentiality
late testing paradigm
late feedback
to customer and engineer
minimal risk management
for customer and engineer

4. The “V” LIFE-CYCLE Requirements Acceptance Test System Design
Integration Test
Detailed Design
Module Test
Implementation

5. Analysis of the V-Shaped Life-Cycle
Improves the testing paradigm
==> Quality Assurance
Does NOT really improve:
sequentiality
feedback
risk management (during development)

6. INCREMENTAL DEVELOPMENT Requirements Global System Design Detailed D.
Implem.
Implem.
Implem.
Testing
Testing
Testing
Maintenance

7. Analysis of Incremental Development
Assumes independent subsystems!
Improves (by delivering smaller units):
feedback: stepwise
testing
Avoids monolithic product
Does not really improve:
risk management during development
sequentiality: subsystems

8. (Rapid) Prototyping Goals: break away from sequentiality
speed up feedback
minimize risks for
customer and engineer
incomplete but executable
cheap and fast

9. Prototyping Definition (A. Davis):
A prototype is a partial implementation of a system, constructed primarily to enable customer, user, or developer to learn about the problem or its solution.
Types:
evolutionary / throw-away
horizontal / vertical

10. Horizontal Prototypingf1 fn
user
hardware

11. Vertical Prototyping f1 fn
user
hardware

12. Analysis of Pure Prototyping
Improvements:
breaks sequentiality
supports fast feedback
opportunity for risk management
Problems:
missing organisational structure
==> combine with a life-cycle

13. The Spiral Model Goals: risk management compatible mix between
clear structure (life-cycle) &
flexible prototyping
supports fast feedback & quality assurance

14. risk analysis p r o t o t y p e s evaluate alternatives,
identify & resolve risks
determine objectives,
alternatives,
constraints
risk analysis
p r o t o t y p e s
principles
req. plan
require-
system
ments
dev.
detailed
design
design
plan
integ.
plan
implement
plan the next
phase
test &
install
develop &
verify product

15. End of Section 1c
coming up:
methodologies
for analysis &
design