Question

What is Software Process Model (life cycle models)

Answer 1

Software Process : A set of related activities which result in production of a software . It may be creating a system or modifying an existing system. Any software process must include the following four activities .

1. Software specification (or requirements engineering): it includes defining the main functionalities of the software and the constrains around them.
2. Software design and implementation: it tells about the software to be designed and programmed.
3. Software verification and validation: Then the designed software must conforms to it’s specification and meets the customer needs.
4. Software evolution (software maintenance): Market requirements changes very frequently and the software is to be modified to meet customer requirements.

A process not only includes the activities in it but also the process description like product , roles, Pre and Post conditions. It is a complex activity and involves lots of decisions. And each organisation generally developes its own model depending on its requirements .

Software Process Models: A software process model is a simplified representation of a software process. Each model represents a process from a specific perspective.The simple purpose of these procedures is to offer a customized software development as per the requirements. Sometimes they are also known as software developement life cycle(SDLC) methodologies .There are various types of models :

1. Waterfall model: When we have a structured process and when our requirements are clear as in critical sytems which need detailed, precise, and accurate documents to decribe the system to be produced. It is not good when requirements are not clear and if they constantly change and also not susceptible for customer interaction.The phases of the waterfall model are: Requirements, Design, Implementation, Testing, and Maintenance.
2. Prototype model: This model is used for the developement of an early sample, or release of a product built to test a concept .This is very useful when requirements aren’t clear. Although it needs good tools ,quick development and high costs.The phases of a prototype are:Establish objectives,Define prototype functionality,Develop the prototype,Evaluate the prototype.​​

3. Incremental & Iterative:  They are well suited for large projects and are less expensive to the change of requirements because they support customer interactions with each increment .They don’t fit into small projects or well structured projects.The phases of iterative development are:Inception,Elaboration,Construction,Transition.

4. Spiral:It is good for for high risky or large projects where the requirements are ambiguous.The project’s success is highly dependent on the risk analysis phase. It doesn’t work well for smaller projects.Each loop in the spiral represents a phase. Each loop is split into four sectors: Objective setting,Risk assessment and reduction,Development and validation,Planning.

5. Agile:It suits small-medium size project, with rapidly changes in the requirements as customer is involved during each phase.Very limited planning is required to get started with the project. There are a number of different agile methods available such as: Scrum, Crystal, Agile Modeling (AM), Extreme Programming (XP), etc.