- Because of rapidly changing business environments, businesses have to respond to new opportunities and competition.
- This requires software and rapid development and delivery is not often the most critical requirement for software systems.
- Businesses may be willing to accept lower quality software if rapid delivery of essential functionality is possible.
Requirements
- Because of the changing environment, it is often impossible to arrive at a stable, consistent set of system requirements.
- Therefore a waterfall model of development is impractical and an approach to development based on iterative specification and delivery is the only way to deliver software quickly.
An iterative development process
Advantages of incremental development
- Accelerated delivery of customer services. Each increment delivers the highest priority functionality to the customer.
- User engagement with the system. Users have to be involved in the development which means the system is more likely to meet their requirements and the users are more committed to the system.
Problems with incremental development
- Management problems
- Progress can be hard to judge and problems hard to find because there is no documentation to demonstrate what has been done.
- Contractual problems
- The normal contract may include a specification; without a specification, different form of contract have to used.
- Validation problems
- without a specification, what is the system test against?
- Maintenance problems
- Continual change tends to corrupt software structure making it more expensive to change and evolve to meet new requirements.
- Prototyping
- For some large systems, incremental iterative development and delivery may be impractical; this is especially true when multiple teams are working on different sites.
- prototyping, where an experimental system is developed as a basis for formulating the requirements may be used. this system thrown away when system specification has agreed.
Incremental development and prototyping
Conflicting objectives
- incremental development is to deliver a working system to end user.
