Spiral Development Method

The "spiral" form of software development or spiral development method was created by the famous software engineering researcher Dr. Barry Boehm. Dr. Boehm is also a pioneer in software cost estimating, and the creator of the well-known COCOMO and COCOMO II cost-estimating tools. The spiral method was first discussed in the 1980s and began to attract users, primarily in the large-systems domain.

In 2006 the Department of Defense formally endorsed the spiral method, and in fact has specified that the spiral approach be utilized on some new and large software projects that are out to bid. This endorse­ment by the Department of Defense is going to have a major influence on the defense contracting community.

Spiral development is a form of iterative development, but it includes some noteworthy special features. As with the other forms of iterative development, the overall set of features for a large application are divided into subsets, each of which will be developed separately. For a 10,000-function point application, there would probably be four subsets, each of 2500 function points in size. For each subset or iteration, a spiral software project includes four large phases:

• Planning
• Risk analysis
• Engineering
• Customer evaluation

The most significant difference between the spiral approach and other forms of iterative development is the "risk analysis" phase. This activity is intended to consider every known technical risk that can affect the outcome of the project, and find solutions for as many as possible.

Risk analysis was not usually a formal part of the older waterfall approach, and is missing from some of the Agile and object-oriented methods too. However, it is a valuable adjunct to the development pro­cess for large systems in the 10,000-function point size range. These large applications have traditionally had the highest failure rates and the longest schedule delays of almost any kind of engineered product. Therefore, the inclusion of a risk-analysis phase is a step in the right direction. The only caveat about the risk analysis phase is that the skill set needed to perform an effective risk analysis is not very common.

Questionnaire:

• Explain about the spiral development method?