Cleanroom Software Engineering Getting it right the first time

A Spectrum of Methods Less Formal More Formal Cleanroom OCL and Z Traditional Models: Waterfall, Spiral, Incremental Agile Methods: FDD and SCRUM

Characteristics of Formal Methods Well-defined specification language Typically based on set-theoretical concepts Emphasis on verification Of program correctness Of completeness of description Of refinements to different abstractions Testing/Debugging De-emphasized Process idea borrowed from manufacturing— worth the cost to ensure process delivers acceptable products rather than remove defects to achieve quality

Why Use Cleanroom Process? Claims Verification and testing are synergistic Reasoning faults are “easier to find” than debugging faults Testing based on usage scenarios focuses on “important” errors Not all faults are of equal significance Bottom Line: software developed under the cleanroom process has fewer errors

The Cleanroom Approach Based on the Incremental Process Model with the twist that formal verification is applied to engineering models and the code. Subprocesses System Engineering, Requirements Gathering, Test Planning, Box Structure Specification, Formal Design, Correctness Verification, Code Generation, Code Inspection and Verification, Statistical Usage Testing, Certification

Additional Points of Emphasis Why the cleanroom process is not widely used (pg 797) Stereotyped perception, departure from standard practice, and process maturity How cleanroom differs from OO development (pg 800) Statistical QC, mathematical verification, usage- driven testing. Functional Specification Types (pg 801) Black Box (concerned only with I/O) State Box (similar to a UML class diagram) Clear Box (procedural design, e.g., pseudocode)