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Harlan Mills and the Cleanroom Method: Enhancing Software Engineering

Explore the Cleanroom method developed by Harlan Mills for industrial use, emphasizing systematic programming and design verification processes. Learn about Box Structures, Design Verification, and Verification Techniques. Discover the industrial applications and results of using Cleanroom in software development.

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Harlan Mills and the Cleanroom Method: Enhancing Software Engineering

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  1. Cleanroom Method CS 415, Software Engineering II Mark Ardis, Rose-Hulman Institute March 20, 2003

  2. Outline • Harlan Mills • Cleanroom method • Industrial use of cleanroom

  3. Harlan Mills 1919 - 1996

  4. Mathematics and Programming • Roman accounting • "to go from programming as an instinctive, intuitive process to a more systematic, constructive process"

  5. Cleanroom Method • Incremental (spiral) • Box structure specification and design • Design verification • No debugging • Statistical testing

  6. Box Structures • Black boxes: behavior only • State Boxes: behavior + state • Clear boxes: procedures

  7. S1S2...Sn R stimulus history  response Black Boxes

  8. State Boxes State Data S R stimulus, old state  response, new state

  9. Clear Boxes State Data S R Procedures stimulus, old state  response, new state

  10. Box Description Language (BDL) • Invocation: use <type> <name> <args> • Sequence: do B1; B2od • Alternation: if <cond> then B1else B2fi • Iteration: while <cond> do B od

  11. Box Structure Hierarchy BB SB CB BB BB BB SB SB SB CB CB CB

  12. Cartoon of the Day (1/3)

  13. Cartoon of the Day (2/3)

  14. Cartoon of the Day (3/3)

  15. Design Verification • Procedures in BDL are checked for correctness with their higher-level descriptions • All boxes (and all procedures) describe functions • Formal proofs of correctness can be performed (but often informal proofs are done, instead)

  16. Verification of Sequence Given a high-level function [f] for statement: do [g]; [h] od Does [g] followed by [h] compute the same function as [f]? Example: [f](x) = 2 * x + 7 [g](x) = 2 * x [h](x) = x + 7

  17. Verification of Selection Given a high-level function [f] for statement: if <cond> then[g]else[h]fi • Whenever <cond> is true, does [g] compute the same function as [f]? • Whenever <cond> is false, does [h] compute the same function as [f]?

  18. Verification of Iteration Given a high-level function [f] for statement: while <cond> do[g]od • Whenever <cond> is true, does [g] followed by [f] compute the same function as [f]? • Does the loop always terminate? • Whenever <cond> is false, does the empty function compute the same function as [f]?

  19. Usage Testing • Develop an operational profile of use • Generate random tests that fit the probabilities

  20. Example

  21. Test Generation

  22. Industrial Use • Used in a few areas of IBM • Used by some military contractors • Tried at NASA

  23. Software Engineering Laboratory (SEL) • Joint program of NASA Goddard Space Center, Computer Sciences Corporation, and the University of Maryland • Conduct experiments and case studies on new software technology

  24. SEL Experience • First trial at University of Maryland • controlled experiment (10 experiment teams,5 control teams • FORTRAN • 1.5 KLOC • 3 case studies at Goddard • flight-dynamics ground support systems • FORTRAN • 40 KLOC, 22 KLOC, 160 KLOC

  25. SEL Results – University Experiment • Cleanroom teams • use fewer computer resources • satisfy requirements more successfully • make higher percentage of scheduled deliveries

  26. SEL Results – Goddard • More effort spent in design • Better reliability of final product • Smaller projects achieve higher productivity, but large project just average

  27. Summary • Cleanroom may be an effective method for achieving higher reliability • Requires some culture change (no debugging) • Still being investigated by researchers and practitioners

  28. References Victor Basili and Scott Green, "Software process evolution at the SEL", IEEE Software 11(4), 58-66, July 1994.

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