Spiral Model, advantages and disadvantages of spiral model in software engineering

Spiral Model, advantages and disadvantages of the spiral model in software engineering.

What is a spiral model?

The spiral model is a combination of waterfall, incremental, iterative and prototype model. It is mostly used for big projects where continuous changes are required.

Phases of the spiral model

Planning
Risk analysis
Engineering and Construction
Evaluation

Phase	Activities	Deliverable
Planning	≡ Requirement gathering ≡ Requirement analysis ≡ Requirement specification ≡ Requirement negotiation ≡ Requirement modeling ≡ Requirement Management	Software Requirement Specification document (SRS)
Risk Analysis	≡ Risk identification ≡ Prioritization of risk ≡ Risk reduction (Mitigation) ≡ Risk impact reduction ≡ Risk monitoring	Risk detailed document
Engineering	≡ Development ≡ Testing	≡ Code ≡ Test cases document, Test report document ≡ Fault report document
Evaluation	≡ Initial Validation by stakeholders ≡ Final Validation by customer	Evaluation report document

What are the advantages of the spiral model?

≡ Ensure risk reduction

≡ Useful for large projects

≡ Changes can be handled in the next iteration/loop.

≡ Most suitable for real-time systems

What are the disadvantages of the spiral model?

≡ Expert required for risk reduction

≡ More costly

≡ Not suitable for small projects

≡ Project duration can be infinite because of its spiral behavior.

≡ Project cost can be infinite because of its spiral behavior

≡ Documentation can be very large

arial, helvetica, sans-serif;”>≡ Not suitable for the projects with low risk

When to use the spiral model?

≡ When the risk is medium or high

≡ When software is to be used in a very sensitive and dangerous environment.

≡ For real-time systems

≡ For large projects

≡ When requirements are not clear

≡ When changes in the software can be expected at any time.

Comparison of spiral model and waterfall model

Properties	Spiral	Waterfall
Objectives	High Assurance	High Assurance
Planning in early stage	Yes	Yes
Returning to an earlier phase	Yes	No
Handle Large-Project	Appropriate	Not Appropriate
Time-Frame	Long	Very Long
Working software availability	At the end of every iteration	At the end of the life-cycle
Risk Involvement	Medium to high risk	High
Software Team size	Large Software Team	Large Software Team
Customer control over administrator	Yes	Very Low
Maintenance	Typical	Least
Time Duration	Long	Long
Re-usability	To some extent	Least possible
Framework Type	Linear + Iterative	Linear
When Testing?	At the end of the engineering phase	After completion of development phase
Maintenance	Yes	Least Maintainable
Detailed Documentation	Yes	Necessary
Overlapping Phases	No	No

Comparison of spiral model and incremental model

Properties	Spiral	Incremental
Objectives	High Assurance	Rapid Development
Planning in early stage	Yes	Yes
Returning to an earlier phase	Yes	Yes
Handle Large-Project	Appropriate	Not Appropriate
Time-Frame	Long	Long
Working software availability	At the end of every iteration	At the end of every iteration
Risk Involvement	Medium to high risk	Low
Software Team size	Large Software Team	Not Large Software Team
Customer control over administrator	Yes	Yes
Maintenance	Typical	Promotes Maintainability
Time Duration	Long	Very long
Re-usability	To some extent	To some extent
Framework Type	Linear + Iterative	Linear + Iterative
When Testing?	At the end of the engineering phase	After every iteration
Maintenance	Yes	Maintainable
Detailed Documentation	Yes	Yes but not much
Overlapping Phases	No	Yes

Comparison of spiral model and RAD

Properties	Spiral	Rad
Objectives	High Assurance	Rapid development
Planning in early stage	Yes	No
Returning to an earlier phase	Yes	Yes
Handle Large-Project	Appropriate	Not Appropriate
Time-Frame	Long	Short
Working software availability	At the end of every iteration	At the end of the life cycle
Risk Involvement	Medium to high risk	Low
Software Team size	Large Software Team	Small Software Team
Customer control over administrator	Yes	Yes
Maintenance	Typical	Easily Maintained
Time Duration	Long	Short
Re-usability	To some extent	Yes
Framework Type	Linear + Iterative	Linear
When Testing?	At the end of the engineering phase	After completion of development
Maintenance	Yes	Easily Maintainable
Detailed Documentation	Yes	Limited
Overlapping Phases	No	Yes