The incremental development process in Cleanroom software engineering

摘要

The objective of this paper is to present the theoretical basis and practical application of incremental development in the Cleanroom software engineering process. Incremental development is based on the mathematical principle of referential transparency. Cleanroom uses incremental development to build systems in a succession of cumulative subsets of user function. The increments accumulate top-down into the final product in a development and certification pipeline. Increment planning occurs after top-level specification, and results in a construction plan for the software. Factors determining the composition of increments include clarity of requirements, usage probability of user functions, reliability requirements for subsystems, coordination with the hardware development schedule, dependencies between functions, complexity, reuse, or other factors that pose risks to the project. Each increment involves a complete development and certification cycle. The first increment is a minimal system, and the final increment is the complete system. User feedback on each increment is a gauge on whether the right system is being built, and quality measures in each increment are a gauge on whether the system is being built right. Benefits of incremental development include customer feedback on the evolving system, intellectual control of the technical work, and management control of the schedule and budget. While incremental development may be used with other development methods, it is particularly effective when used with the formal methods in the Cleanroom process.