and Process Model • Process: A structured set of activities required to develop a software system Think about this as an “object” • Process Models: A simplified representation of the activities and relationships in a process Think about this as an “class”
of Process (Strategies) § Plan-driven all process activities are established in advance and progress is measured against a plan (a contract). § Agile, planning is incremental, and it is easier to change the process to reflect changing customer requirements.
Waterfall Model § Key idea: Separate and distinct phases of specification and development. A phase has to be complete before moving onto the next phase. § Type: Linear model. § Recommended for: Embedded systems and Large systems(developed by several partner companies) § Disadvantage: difficulty of accommodating change after the process is underway.
V-Model § Key idea: It is an extension of Waterfall where instead of moving down in a linear way, the process steps are bent upwards after the coding phase. While tests are just one of five steps in Waterfall, it looks like practically half of the process in V-model. § Type: Linear model. § Recommended for: well-suited for projects that must maintain a strict deadline and meet key milestone dates throughout the process. Example: medical device industry § Disadvantage: same that waterfall
Incremental Model § Key idea: split each activity in pieces. § Type: Iterative model (it could include parallel). § Recommended for: Facilitate getting customer feedback on the development work that has been done. § Disadvantages: (1) it could not cost-effective to produce documents that reflect every version of the system; (2) System structure tends to degrade as new increments are added. Unless time and money is spent on refactoring to improve the software, regular change tends to corrupt its structure.
§ Definition: a prototype is an initial version of a system used to demonstrate concepts and try out design options. § Evolutionary model § Recommended for: a prototype can be used to help with requirements elicitation and validation; or in design processes to explore options and develop a UI design.
Spiral Model • Key idea: High amount of risk analysis hence, avoidance of Risk is enhanced. • Evolutionary model • Recommended for: (1) Good for large and mission- critical projects. (2) Strong approval and documentation control. (3) Significant changes are expected (research and exploration). • Doesn’t work well for smaller projects. • Doesn’t work well when users are unsure of their needs • Doesn’t work well when requirements are complex