The cleanroom software engineering process is a
software development process
In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software deve ...
intended to produce software with a certifiable level of
reliability. The cleanroom process was originally developed by
Harlan Mills
Harlan D. Mills (May 14, 1919 – January 8, 1996) was Professor of Computer Science at the Florida Institute of Technology and founder of Software Engineering Technology, Inc. of Vero Beach, Florida (since acquired by Q-Labs). Mills' contr ...
and several of his colleagues including Alan Hevner at
IBM. The focus of the cleanroom process is on defect prevention, rather than defect removal. The name "cleanroom" was chosen to evoke the
cleanroom
A cleanroom or clean room is an engineered space, which maintains a very low concentration of airborne particulates. It is well isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientif ...
s used in the electronics industry to prevent the introduction of defects during the fabrication of
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
s. The cleanroom process first saw use in the mid to late 1980s. Demonstration projects within the military began in the early 1990s. Recent work on the cleanroom process has examined fusing cleanroom with the automated verification capabilities provided by specifications expressed in
CSP.
Central principles
The basic principles of the cleanroom process are
;Software development based on
formal methods
In computer science, formal methods are mathematically rigorous techniques for the specification, development, and verification of software and hardware systems. The use of formal methods for software and hardware design is motivated by the exp ...
: Software tool support based on some mathematical formalism includes
model checking
In computer science, model checking or property checking is a method for checking whether a finite-state model of a system meets a given specification (also known as correctness). This is typically associated with hardware or software system ...
,
process algebras, and
Petri nets
A Petri net, also known as a place/transition (PT) net, is one of several mathematical modeling languages for the description of distributed systems. It is a class of discrete event dynamic system. A Petri net is a directed bipartite graph that ...
. The
Box Structure Method might be one such means of specifying and designing a software product.
Verification that the design correctly implements the specification is performed through team review, often with software tool support.
;Incremental implementation under
statistical quality control: Cleanroom development uses an
iterative
Iteration is the repetition of a process in order to generate a (possibly unbounded) sequence of outcomes. Each repetition of the process is a single iteration, and the outcome of each iteration is then the starting point of the next iteration. ...
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
An examination (exam or evaluation) or test is an educational assessment intended to measure a test-taker's knowledge, skill, aptitude, physical fitness, or classification in many other topics (e.g., beliefs). A test may be administered verba ...
: 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.
References
Further reading
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External links
An introduction
{{Software engineering
Software quality