Spiral Model

Risk-Driven Process Model Generator

“The spiral development model is a risk-driven process model generator. It is used to guide multi-stakeholder concurrent engineering of software-intensive systems. It has two main distinguishing features. One is a cyclic approach for incrementally growing a system's degree of definition and implementation. The other is a set of anchor point milestones for ensuring stakeholder commitment to feasible and mutually satisfactory system solutions.” [Boehm 2000]

Typical Cycle of the Spiral

• Identification of
  • objectives (of the portion of the product being elaborated)
  • alternative means of implementing this portion of the product (design A, design B, buy)
  • constraints imposed on the application of the alternatives (cost, schedule, copyright)
  
  
  
• Evaluate the alternatives relative to the objectives and constraints
  • Identify areas of uncertainty that are significant sources of risk
  • Evaluate the risks (e.g., by prototyping, simulation, benchmarking)
  
  
  
• The next step is determined by the relative remaining risks. Each level of software specification and development is followed by a validation step.
  
  
  
• Each cycle is completed by the preparation of plans for the next cycle and a review involving the primary people or organizations concerned with the product. The review's major objective is to ensure that all concerned parties are mutually committed to the approach for the next phase.

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