The opportunistic approach is what occurs when an organization does not follow good engineering practices. It does not acknowledge the importance of working out the requirements and the design before implementing a system The design of software deteriorates faster if it is not well designe Since there are no plans, there is nothing to aim towards There is no explicit recognition of the need for ystematic testing and other forms of quality assurance The above problems make the cost of developing and maintaining software very high www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process 6
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 6 The opportunistic approach … is what occurs when an organization does not follow good engineering practices. • It does not acknowledge the importance of working out the requirements and the design before implementing a system. • The design of software deteriorates faster if it is not well designed. • Since there are no plans, there is nothing to aim towards. • There is no explicit recognition of the need for systematic testing and other forms of quality assurance. • The above problems make the cost of developing and maintaining software very high
The waterfall model Requirements athering ar Definition 图, Specification g Implementation Integration and Deployment Maintenance www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 7 The waterfall model V & V Requirements Gathering and Definition V & V Specification V & V Design V & V Implementation V & V Maintenance V & V Integration and Deployment
The waterfall model The classic way of looking at S.E. that accounts for the importance of requirements, design and quality assurance. The model suggests that software engineers should work in a series of stages Before completing each stage, they should perform quality assurance(verification and validation) The waterfall model also recognizes, to a limited extent that you sometimes have to step back to earlier stages www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process 8
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 8 The waterfall model The classic way of looking at S.E. that accounts for the importance of requirements, design and quality assurance. • The model suggests that software engineers should work in a series of stages. • Before completing each stage, they should perform quality assurance (verification and validation). • The waterfall model also recognizes, to a limited extent, that you sometimes have to step back to earlier stages
Limitations of the waterfall model The model implies that you should attempt to complete a given stage before moving on to the next stage -Does not account for the fact that requirements constantly change - lt also means that customers can not use anything until the entire system is complete The model makes no allowances for prototyping It implies that you can get the requirements right by simply writing them down and reviewing them The model implies that once the product is finished everything else is maintenance www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 9 Limitations of the waterfall model • The model implies that you should attempt to complete a given stage before moving on to the next stage —Does not account for the fact that requirements constantly change. —It also means that customers can not use anything until the entire system is complete. • The model makes no allowances for prototyping. • It implies that you can get the requirements right by simply writing them down and reviewing them. • The model implies that once the product is finished, everything else is maintenance
The phased-release model Phase 1 Gathering and Definition Implementation Specification Integration and Planning & Phase 2 Implementation Integration and Depl oyme www.oseng.com O Lethbridge/Laganiere 2001 Chapter Il: Managing the Software Process
© Lethbridge/Laganière 2001 Chapter 11: Managing the Software Process 10 The phased-release model V & V Requirements Gathering and Definition V & V Specification V & V Design V & V Implementation V & V Planning Phase 1 V & V Design V & V Implementation Phase 2 etc ... V & V Integration and Deployment V & V Integration and Deployment