Cleanroom Software Engineering Cont...

The Cleanroom Software Engineering process is a software development process intended to produce software with a certifiable level of reliability. The focus of the Cleanroom process is on defect prevention, rather than defect removal. The name Cleanroom was chosen to evoke the cleanrooms used in the electronics industry to prevent the introduction of defects during the fabrication of semiconductors.

Central principles of Cleanroom Software Engineering :
- Software development based on formal methods
Cleanroom development makes use of the Box Structure Method to specify and design a software product. Verification that the design correctly implements the specification is performed through team review.
- Incremental implementation under statistical quality control
Cleanroom development uses an iterative approach, in which the product is developed in increments that gradually increase the implemented functionality. The quality of each increment is measured against pre-established standards to verify that the development process is proceeding acceptably. A failure to meet quality standards results in the cessation of testing for the current increment, and a return to the design phase.
- Statistically sound testing
Software testing in the Cleanroom process is carried out as a statistical experiment. Based on the formal specification, a representative subset of software input/output trajectories is selected and tested. This sample is then statistically analyzed to produce an estimate of the reliability of the software, and a level of confidence in that estimate.

Advantages of Cleanroom Approach :
- Proven Practice : Several major products have been developed using Cleanroom and delivered to customers.
- Low Error Rate, highly reliable code.
- Increased Productivity.
- Can Be Incorporated Within A Quality Management Program Such As CMM Or ISO 9000.

Why are Cleanroom Techniques Not Widely Used ?
- Some people believe cleanroom techniques are too theoretical, too mathematical, and too radical for use in real software development.
- Relies on correctness verification and statistical quality control rather than unit testing (a major departure from traditional software development).
- Organizations operating at the ad hoc level of the Capability Maturity Model, do not make rigorous use of the defined processes needed in all phases of the software life cycle.