Software Myths Software is easy to change Computers provide greater reliability than the devices they replace. Testing software or ‘proving’ software correct can remove all the errors. Reusing software increases safety. Software can work right the first time. Software can be designed thoroughly enough to avoid most integration problems. Software with more features is better software. Aim is to develop working programs.

Generic Software Process Models There are many different software process models. Here are just four The waterfall model Separate and distinct phases of specification and development; (more below) Evolutionary development Specification and development are interleaved (more below) Formal transformation A mathematical system model is formally transformed to an implementation Reuse-based development The system is assembled from existing components

System and software design Implementation and unit testing The Waterfall Model The waterfall model has separate and distinct phases of specification and development. These are: Requirements analysis and definition System and software design Implementation and unit testing Integration and system testing Operation and maintenance

Waterfall Model

Advantage Progress can be conclusively identified (through the use of milestones) by both vendor and client. Ensures minimal wastage of time and effort. Reduces the risk of schedule slippage, or of customer expectations not being met.

Prototyping Model A type of development in which emphasis is placed on developing prototypes early in the development process to permit early feedback and analysis in support of the development process.”

As a requirements artifact to initially envision the system. Need for prototyping As a requirements artifact to initially envision the system. As a design artifact that enables us to explore the solution space of your system. A vehicle for you to communicate the possible UI design(s) of your system. A potential foundation from which to continue developing the system

Prototyping Process Functionality Evaluate Goals Develop

Spiral Model The Spiral Development ( or Lifecycle) Model is a systems development method used in information technology. It combines the features of the prototyping model and the waterfall model. It is favored for large, expensive, and complicated models.

A preliminary design is created for the new system. Steps of the Spiral Model Define the problem with as much detail as possible by interviewing the client and potential users of the system, as well as, studying any existing system. A preliminary design is created for the new system. A first prototype of the new system is constructed from the preliminary design and is a scaled down version of the final product.