The phased-release model It introduces the notion of incremental development After requirements gathering and planning, the project should be broken into separate subprojects, or phases Each phase can be released to customers when ready Parts of the system will be available earlier than when using a strict waterfall approach However, it continues to suggest that all requirements be finalized at the start of development www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 11 The phased-release model It introduces the notion of incremental development. • After requirements gathering and planning, the project should be broken into separate subprojects, or phases. • Each phase can be released to customers when ready. • Parts of the system will be available earlier than when using a strict waterfall approach. • However, it continues to suggest that all requirements be finalized at the start of development
The spiral model Release 2 Release 1 Revew Anal ysis of risk Prototy pe Requirements Integration and deploy ment Specific ati Implementation Desig www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 12 The spiral model Requirements Specification Design Implementation Prototype Release 1 Release 2 Review Analysis of risk Integration and deployment
The spiral model It explicitly embraces prototyping and an iterative approach to software development. Start by developing a small prototype Followed by a mini-waterfall process primarily to gather requirements Then, the first prototype is reviewed In subsequent loops, the project team performs further requirements, design, implementation and review The first thing to do before embarking on each new loop is risk analysis Maintenance is simply a type of on-going development www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process 13
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 13 The spiral model It explicitly embraces prototyping and an iterative approach to software development. • Start by developing a small prototype. • Followed by a mini-waterfall process, primarily to gather requirements. • Then, the first prototype is reviewed. • In subsequent loops, the project team performs further requirements, design, implementation and review. • The first thing to do before embarking on each new loop is risk analysis. • Maintenance is simply a type of on-going development
The evolutionary model Time Development Activit www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process 14
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 14 The evolutionary model Time Development Activity
The evolutionary model It shows software development as a series of hills, each representing a separate loop of the spiral. Shows that loops, or releases, tend to overlap each other Makes it clear that development work tends to reach a peak, at around the time of the deadline for completion Shows that each prototype or release can take different amounts of time to deliver -differing amounts of effort www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process 15
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 15 The evolutionary model It shows software development as a series of hills, each representing a separate loop of the spiral. • Shows that loops, or releases, tend to overlap each other. • Makes it clear that development work tends to reach a peak, at around the time of the deadline for completion. • Shows that each prototype or release can take —different amounts of time to deliver; —differing amounts of effort