Spiral - model

Spiral - model

§ This model of development combines the features of the prototyping model and the waterfall model. The spiral model is favored for large, expensive, and

complicated projects.
§ The spiral model is similar to the incremental model, with more emphases placed on risk analysis. The spiral model has four phases: Planning, Risk

Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral,

starting in the planning phase, requirements is gathered and risk is assessed. Each subsequent spiral builds on the baseline spiral.
§ Requirements are gathered during the planning phase. In the risk analysis phase, a process is undertaken to identify risk and alternate solutions. A

prototype is produced at the end of the risk analysis phase.
§ Software is produced in the engineering phase, along with testing at the end of the phase. The evaluation phase allows the customer to evaluate the

output of the project to date before the project continues to the next spiral.
§ In the spiral model, the angular component represents progress, and the radius of the spiral represents cost.

Advantages
§ High amount of risk analysis.
§ Risks are explicitly assessed and resolved throughout the process
§ Focus on early error detection and design flaws.
§ Good for large and mission-critical projects.
§ Software is produced early in the software life cycle.

Disadvantages
§ Can be a costly model to use.
§ Risk analysis requires highly specific expertise.
§ Project’s success is highly dependent on the risk analysis phase.
§ Doesn’t work well for smaller projects.

Strengths:
•It promotes reuse of existing software in early stages of development
•Allows quality objectives to be formulated during development
•Provides preparation for eventual evolution of the software product
•Eliminates errors and unattractive alternatives early.
•It balances resource expenditure.
•Doesn’t involve separate approaches for software development and software maintenance.
•Provides a viable framework for integrated Hardware-software system development.

Weakness:
•This process needs or usually associated with Rapid Application Development, which is very difficult practically.
•The process is more difficult to manage and needs a very different approach as opposed to the waterfall model (Waterfall model has management techniques like

GANTT charts to assess)