What is the Spiral What is the Spiral Development Model?Development Model?

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What is it?What is it?

The Spiral Development ( or Lifecycle) Model The Spiral Development ( or Lifecycle) Model is a systems development method used in is a systems development method used in information technology.information technology.

It combines the features of the prototyping It combines the features of the prototyping model and the waterfall model.model and the waterfall model.

It is favored for large, expensive, and It is favored for large, expensive, and complicated models.complicated models.

Steps of the Spiral ModelSteps of the Spiral Model

1.1. Define the problem with as much detail as Define the problem with as much detail as possible by interviewing the client and possible by interviewing the client and potential users of the system, as well as, potential users of the system, as well as, studying any existing system.studying any existing system.

2.2. A preliminary design is created for the new A preliminary design is created for the new system.system.

3.3. A first prototype of the new system is A first prototype of the new system is constructed from the preliminary design and constructed from the preliminary design and is a scaled down version of the final product.is a scaled down version of the final product.

Steps of the Spiral ModelSteps of the Spiral Model

4. A second prototype is derived by the 4. A second prototype is derived by the following procedurefollowing procedure

Evaluate the first prototype for strengths, Evaluate the first prototype for strengths, weaknesses and risksweaknesses and risks

Define the requirements of the 2Define the requirements of the 2ndnd prototype prototype Plan and design the 2Plan and design the 2ndnd prototype prototype Construct and test the 2Construct and test the 2ndnd prototype prototype

Steps of the Spiral ModelSteps of the Spiral Model

5.5. At this point the customer may decide to At this point the customer may decide to scrap the whole project if the risk is too high.scrap the whole project if the risk is too high.

Development cost overrunsDevelopment cost overruns Operating-cost miscalculationOperating-cost miscalculation Other factors that might result in a substandard Other factors that might result in a substandard

productproduct

Steps of the Spiral ModelSteps of the Spiral Model

6.6. Evaluate the current prototype in the same Evaluate the current prototype in the same way as the previous prototype and create way as the previous prototype and create another one if neededanother one if needed

7.7. Iterate the proceeding steps until the Iterate the proceeding steps until the customer is satisfied that the current customer is satisfied that the current prototype represents the final product.prototype represents the final product.

8.8. Construct the final systemConstruct the final system

Steps of the Spiral ModelSteps of the Spiral Model

9. The final system is thoroughly evaluated and 9. The final system is thoroughly evaluated and tested and routine maintenance is carried out tested and routine maintenance is carried out for the life of the product. for the life of the product.

AdvantagesAdvantages

Estimates of the budget and schedule become Estimates of the budget and schedule become more realistic as work progresses because of more realistic as work progresses because of the questions that have been raisedthe questions that have been raised

Easier to cope with the changes inherent to Easier to cope with the changes inherent to software developmentsoftware development

Software engineers can start working on the Software engineers can start working on the project earlier rather than wading through a project earlier rather than wading through a lengthy early design process.lengthy early design process.

DisadvantagesDisadvantages

Estimates of budget and time are harder to Estimates of budget and time are harder to judge at the beginning of the project since the judge at the beginning of the project since the requirements evolve through the processrequirements evolve through the process

So What?So What?

This semester you will use the Spiral Model This semester you will use the Spiral Model (mostly) with 2-3 iterations.(mostly) with 2-3 iterations.

Initially devise your problem statement and Initially devise your problem statement and requirements analysis as thoroughly as requirements analysis as thoroughly as possiblepossible

Create your design specification to reflect your Create your design specification to reflect your first prototype passfirst prototype pass

First and second drafts of each will be turned First and second drafts of each will be turned in to ensure you are doing it right.in to ensure you are doing it right.

So What?So What?

Toward the end of October you will do a small Toward the end of October you will do a small presentation of your prototype and submit your presentation of your prototype and submit your complete documentationcomplete documentation

This will be repeated before Thanksgiving and This will be repeated before Thanksgiving and during finals weekduring finals week

DocumentationDocumentation

When you complete your second drafts you When you complete your second drafts you will amend the original documents.will amend the original documents.

Subsequent submissions will have new Subsequent submissions will have new information appended to documents in new information appended to documents in new sections.sections.

Your final documents will not only reflect Your final documents will not only reflect your final product but the path you took to get your final product but the path you took to get there.there.