Glossary


Spiral Model

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Identification

Spiral Model

Definitions/Uses

2001
Reference /Scacchi, 2001/ Process Models in Software Engineering

Definition/
Use The spiral model of software development and evolution represents a risk-driven approach to software process analysis and structuring /Boehm, 1988a/, /Boehm, 1998b/. This approach, developed by Barry Boehm, incorporates elements of specification-driven, protoype-driven process methods, together with the classic software life cycle. It does so by representing iterative development cycles as an expanding spiral, with inner cycles, denoting early system analysis and prototyping, and outer cycles denoting the classic software life cycle. The radial dimension denotes cumulative development costs, and the angular dimensions denotes progress made in accomplishing each development spiral.
Risk analysis, which seeks to identify situations that might cause a development effort to fail or go over budget/schedule, occurs during each spiral cycle. In each cycle, it represents roughly the levels of effort required for risk analysis. System development in this model therefore spirals out only so far as needed according to the risk that must be managed. Alternatively, the spiral model indicates that the classic software life cycle model need only be followed when risks are greatest, and after early system prototyping as a way of reducing these risks, albeit at increased cost. The insights that the Spiral Model offered has in turned influence the standard software life cycle process models, such as ISO 12207 noted earlier. Finally, efforts are now in progress to integrate computer-based support for stakeholder negotiations and capture of trade-off rationales into an operational for of the WinWin Spiral Model /Boehm, 1998b/.

Rationales The author classifies the Spiral Model as one of the Non-Operational Process Models

1971
Reference /Boehm, 1988a/ A spiral model of software development and enhancement

Definition/
Use

2001
Reference	/Scacchi, 2001/ Process Models in Software Engineering
Definition/ Use	The spiral model of software development and evolution represents a risk-driven approach to software process analysis and structuring /Boehm, 1988a/, /Boehm, 1998b/. This approach, developed by Barry Boehm, incorporates elements of specification-driven, protoype-driven process methods, together with the classic software life cycle. It does so by representing iterative development cycles as an expanding spiral, with inner cycles, denoting early system analysis and prototyping, and outer cycles denoting the classic software life cycle. The radial dimension denotes cumulative development costs, and the angular dimensions denotes progress made in accomplishing each development spiral. Risk analysis, which seeks to identify situations that might cause a development effort to fail or go over budget/schedule, occurs during each spiral cycle. In each cycle, it represents roughly the levels of effort required for risk analysis. System development in this model therefore spirals out only so far as needed according to the risk that must be managed. Alternatively, the spiral model indicates that the classic software life cycle model need only be followed when risks are greatest, and after early system prototyping as a way of reducing these risks, albeit at increased cost. The insights that the Spiral Model offered has in turned influence the standard software life cycle process models, such as ISO 12207 noted earlier. Finally, efforts are now in progress to integrate computer-based support for stakeholder negotiations and capture of trade-off rationales into an operational for of the WinWin Spiral Model /Boehm, 1998b/.
Rationales	The author classifies the Spiral Model as one of the Non-Operational Process Models
1971
Reference	/Boehm, 1988a/ A spiral model of software development and enhancement
Definition/ Use

Identification

Definitions/Uses

See also