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Formal Methods: Industrial Use

Explore the use of formal methods in industrial settings through case studies like IBM CICS project and Tektronix oscilloscope to understand benefits, challenges, and lessons learned for software development.

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Formal Methods: Industrial Use

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  1. Formal Methods: Industrial Use CS 415, Software Engineering II Mark Ardis, Rose-Hulman Institute March 21, 2003

  2. Outline • Controversy over formal methods • Where are formal methods used? • 4 Stories • IBM CICS project • Tektronix oscilloscope • LOTOS at Bell Labs • VFSM at Bell Labs

  3. Controversy Over Formal Methods • DeMillo, Lipton and Perlis "Social Processes and Proofs of Theorems and Programs", CACM, May 1979. • Fetzer "Program Verification: The Very Idea," CACM, September 1988. • The "Gang of 10"

  4. Where are Formal Methods Used? • Safety critical applications • Aviation • Railway transportation • MOD 00-55 • Other high-integrity systems • Application generators • Hardware design

  5. IBM CICS Project • Maintenance of Customer Information Control System (CICS) • Used Z to reverse engineer old code • Found more errors earlier in the lifecycle

  6. Maintenance of CICS • Old (> 30 years) • Large (>500 KLOC) • Multiple languages (assembler and special dialect of PL/I) • Many users • Several configurations

  7. Restructuring of CICS • Necessary first step before Z could be used • Independent of any method

  8. Reverse Engineering • Z specifications derived from: • manuals • developers • code • About half of CICS described in Z (230 KLOC) • Modules added or rewritten later from Z specifications

  9. IBM Development Process • Used standard IBM process, including: • design reviews • code inspections • testing • Used standard IBM programming languages, plus guarded command language • Required training of staff in Z

  10. IBM Training • Used standard IBM courses, including: • discrete mathematics • software engineering workshop • Augmented with Z courses • 4 days for writers • 2 days for readers • 1 day for managers

  11. IBM Results • More time spent in design • Inspections required less preparation, but took longer to conduct • More problems found earlier in design • Fewer problems found in testing • Overall time was 9% less than average • Won Queen's Award for productivity

  12. Cartoon of the Day

  13. Tektronix • Exploratory project • Discovered useful abstractions • Concentrated on process of specification, not product

  14. Tektronix Process • 2 researchers (DeLisle and Garlan) investigated general problem area: • talked to engineers • tried to describe existing devices • Discussed trial specifications with engineers

  15. Tektronix Results • Original descriptions were operational • Researchers found an abstraction (waveform) that clarified roles of hardware and software engineers • Resulting specification yielded insights about tradeoffs: • user interfaces • sampling methods • hw/sw partitioning

  16. Tektronix Lessons • Industrial engineers can understand formal specifications • Abstraction was very valuable in focusing attention on right problem • Specification was a process, not a product

  17. LOTOS at Bell Labs • Some formal methods used in switching applications • SDL • Promela • VFSM • Opportunity to try LOTOS in 1991 • Language Of Temporal Ordering Sequences • New standard for telecommunication protocols

  18. Primitive LOTOS Project • Basic LOTOS difficult to use • too much redundancy • too little redundancy • Primitive LOTOS (PLOTOS) • added declarations • more "C"-like

  19. PLOTOS Results • Used on parts of several projects • Tools were popular • Solved the wrong problem • specification was a verb, not a noun • spaceship theory

  20. PLOTOS Lessons • Software developers in Naperville are an oral culture • work via meetings • very little abstraction • Need to first move to literary paradigm • domain engineering to capture knowledge in writing • domain specific languages to develop formal notations

  21. VFSM at Bell Labs • Manager convinced by a former teacher to try Virtual Finite State Machines (VFSM) • Constructed a compiler to C • Later adapted SPIN for model checking

  22. VFSM Results • Used on several projects • Tools were popular • Solved the right problem • compiled to executable code • testing was the most onerous job of development

  23. VFSM Lessons • Bottom-up development is more easily accepted than top-down • Free lunches are a powerful force • Revolutionary methods need crusaders

  24. Summary • Formal methods provide substantial benefits, but at cost • May be most applicable in established domains • Adoption requires cultural change for many organizations

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