1. Software Project Management
Lecture 2 Software Development Models

2. Overview Introduction Technical plan Software process models
Selecting process model(s)
Software project management

3. Definitions Software Process Software Process Model (Humphrey 1990)
the set of activities, methods, and practices that are used in the production and evolution of software
Software Process Model
one specific embodiment of a software process architecture
(Humphrey 1990)
Software project management

4. Why Modelling? To provide a common understanding
To locate any inconsistencies, redundancies and omissions
To reflect the development goals and provide early evaluation
To assist the development team to understand any special situation
Software project management

5. Project Analysis Methodologies Technologies
Object-Oriented Development (OOD)
Structured System Analysis and Design Method (SSADM)
Jackson Structured Programming (JSP)
Technologies
application-building environments
knowledge-based system tools
Software project management

6. Project Characteristics
data oriented or control oriented system?
general package or application specific?
a particular type of system for which specific tools have been developed?
safety-critical system?
nature of the hardware/software environment?
Software project management

7. Project Risks Product uncertainty Process uncertainty
Resource uncertainty
Software project management

8. Considerations for Project Approach
Control systems
Information systems
General applications
Specialized techniques
Hardware environment
Safety-critical systems
Imprecise requirements
Software project management

9. Technical Plan Contents Constraints Approach Implementation
Implications
Software project management

10. Technical Plan - Constraints
Character of the system to be developed
Risks and uncertainties of the project
User requirements concerning implementation
Software project management

11. Technical Plan - Approach
Software Project Management
Technical Plan - Approach
Selected methodology or process model(s)
Development methods
Required software tools
Target hardware/software environment
The technical plan is typically a mixture of models.
Eg prototyping to resolve some requirements plus V-model for production.
Software project management

12. Technical Plan - Implementation
Development environment
Maintenance environment
Training
Software project management

13. Technical Plan - Implications
Software Project Management
Technical Plan - Implications
Project products and activities
effect on schedule duration and overall project effort
Financial
report used to produce costings
Software project management

14. Software Process Models
Waterfall Model
V Model
Spiral Model
Prototyping Model
Software project management

15. Software Process Models (cont’d)
Phased Development Model
incremental development model
iterative development model
Operational Specification Model
Transformation Model
Software project management

16. Waterfall Model Requirements Analysis System Design Coding Testing
Maintenance
Software project management

17. Waterfall Model (cont’d)
classical
one-shot approach
effective control
limited scope of iteration
long cycle time
not suitable for system of high uncertainty
Software project management

18. V Model Maintenance Requirements Analysis User Acceptance Testing
System Design
System Testing
Unit and
Integration Testing
Program Design
Coding
Software project management

19. V Model (cont’d) Additional validation process introduced
Relate testing to analysis and design
Loop back in case of discrepancy
Software project management

20. Spiral Model (adapted from Boehm 1987)
Cumulative cost
Progress through steps
Determine objectives, alternatives and constraints
Evaluate alternatives; identify and resolve risks
Risk analysis
Risk analysis
Risk analysis
Prototype
Prototype
Prototype
Requirements plan
Concept of operation
Software requirements
System product design
Detailed design
Development plan
Requirements validation
Coding
Integration and Test plan
Design validation
Unit testing
Develop and verify next-level product
Plan next phases
Integration and Test
Acceptance test
Software project management

21. Spiral Model (cont’d) Evolutionary approach
Iterative development combined with risk management
Risk analysis results in “go, re-do, no-go” decision
Software project management

22. Spiral Model (cont’d) Four major activities Planning Risk analysis
Software Project Management
Spiral Model (cont’d)
Four major activities
Planning
Risk analysis
Engineering
Evaluation
Software project management

23. Prototyping Model Goals
meet (some) user requirements at an early stage
reduce risk and uncertainty
verify a design or implementation approach
Should always answer specific questions; goals must be identified
Software project management

24. Classification of Prototype
Software Project Management
Classification of Prototype
Throw-away
After users agree the requirements of the system, the prototype will be discarded.
Evolutionary
Modifications are based on the existing prototype.
Incremental
Functions will be arranged and built accordingly.
Software project management

25. Prototyping Model User YES satisfaction Build prototype NO
User feedback
Software project management

26. Benefits of Prototyping
Learning by doing
Improved communication
Improved user involvement
Clarification of partially-known requirements
Software project management

27. Prototyping Sequences
Requirements gathering
Quick design
Prototype construction
Customer evaluation
Refinement
Loop back to quick design for fine tuning
Product engineering
Software project management

28. Benefits of Prototyping
Software Project Management
Benefits of Prototyping
Demonstration of the consistency and completeness of a specification
Reduced need for documentation
Reduced maintenance costs
Feature constraint
Production of expected results for testing real system
Reduced maintenance costs in the sense that users are less likely to ask for changes after the system goes into its operation. However, when asked for changes, the system is difficult to maintain because the software is usually not well structured.
Software project management

29. Drawbacks of Prototyping
Users sometimes misunderstand the role of the prototype
Lack of project standards possible
Lack of control
Additional expense
Machine efficiency
Close proximity of developers
Software project management

30. Forms of Prototypes Mock-ups Simulated interaction
Partial working model
Software project management

31. Prototype Products Human-computer interface System functionality
Software project management

32. Prototype Changes Three categories Cosmetic (35%) Local (60%)
Software Project Management
Prototype Changes
Three categories
Cosmetic (35%)
screen layout
Local (60%)
screen processing
Global (5%)
multi-parts processing
design review
Software project management

33. Phased Development Reduce cycle time Two parallel systems:
operational system (Release n)
development system (Release n+1)
Two approaches
incremental
iterative
Software project management

34. Incremental Model Break system into small components
Implement and deliver small components in sequence
Every delivered component provides extra functionality to user
Software project management

35. Incremental Model (cont’d)
Arrange requirements in increments
Design and develop increment
Requirements Analysis NO
System
OK?
Validate increment
Integrate increment
YES
Software project management

36. Iterative Model Deliver full system in the beginning
Enhance functionality in new releases
Software project management

37. Iterative Model (cont’d)
Design system version n
n = n+1 NO
System
complete
Develop system version n
Validate system version n
YES
Software project management

38. Combined Incremental and Iterative Model
Every new release includes
extra functionality
enhancement of existing functionality
Popularly used in software industry
Software project management

39. Ranking the Increments
Rank by value to cost ratio
V = value to customer (score 1 -10)
C = cost (score 1- 10)
Value to cost ratio = V/C
Example: Table 4.1
Software project management

40. Advantages of Phased Development
Early feedback
Less possible requirement changes
Early benefits for users
Improved cash flow
Easier to control and manage
Software project management

41. Advantages of Phased Development (cont’d)
Capture early market
Facilitate early training
Can be temporarily abandoned
Increase job satisfaction
Software project management

42. Disadvantages of Phased Development
‘Software breakage’
Reduced productivity
Software project management

43. Operational Specification Model
Executable or translatable specification
Use executables to demonstrate system behaviour
Resolve requirement uncertainties in early stage
Merging functionality and system design
Software project management

44. Transformational Model
Transform a specification into delivered system
Requires automated support
Relies on formal specification method
Software project management

45. Software Project Management
References
Boehm, B. (1987) A sprial model of software development and enhancement, Software Engineering Project Management, p.128–142.
Hughes, B. and Cotterell, M. (1999) Software Project Management, 2nd ed., McGraw Hill.
Humphrey, W. (1990) Managing the Software Process, Addison-Wesley.
Pfleeger, S.L. (1998) Software Engineering Theory and Practice, Prentice Hall
Software project management