Spiral model : System analysis and design

SPIRAL MODEL (SDLC)By:-

Mitul K. Desai – 23

Nishit Modi – 25

Vikram Bajaj - 37

HISTORY

This model was first described by Barry Boehm in his 1986 paper

"A Spiral Model of Software Development and Enhancement".

Boehm describes the spiral model as a "process model generator“.

Here choices were based on project risk.

WHAT IS IT ?

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

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

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

FOUR BASIC ACTIVITIES IN EVERY CYCLE Consider the win conditions of all success-critical stakeholders.

Identify and evaluate alternative approaches for satisfying the win conditions.

Identify and resolve risks that stem from the selected approach(es).

Obtain approval from all success-critical stakeholders, plus commitment to pursue the next cycle.

SPIRAL QUADRANT : 1

Objectives: functionality, performance, hardware/software interface, critical success factors, etc.

Alternatives: build, reuse, buy, sub-contract, etc.

Constraints: cost, schedule, interface, etc.

SPIRAL QUADRANT : 2

Study alternatives relative to objectives and constraints

Identify risks (lack of experience, new technology, tight schedules, poor process, etc.

Resolve risks (evaluate if money could be lost by continuing system development

SPIRAL QUADRANT : 3

Typical activities:

Create a design Review design Develop code Inspect code Test product

SPIRAL QUADRANT : 4

Typical activities:

Develop project plan Develop configuration management plan Develop a test plan Develop an installation plan

ADVANTAGES (STRENGTHS)

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

Easier to cope with the changes inherent to software development

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

DISADVANTAGES (WEAKNESSES)

Time spent for evaluating risks too large for small or low-risk projects.

Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive.

The model is complex.

Risk assessment expertise is required.

WHEN TO USE SPIRAL MODEL

Long-term project commitment unwise because of potential changes to economic priorities.

Users are unsure of their needs.

Requirements are complex.

New product line .

Significant changes are expected (research and exploration).

REFERENCES

http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Spiral_model.html

http://csse.usc.edu/csse/TECHRPTS/1988/usccse88-500/usccse88-500.pdf

http://en.wikipedia.org/wiki/File:Spiral_model_(Boehm,_1988).svg