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VCC Case Study: Single-lane Bridge Problem

Summer School on Software Engineering and Verification (SSSEV) July 17-27, Moscow, Russia. VCC Case Study: Single-lane Bridge Problem . Formal2Normal team: Andrey Dereza * Anatoliy Gorbenko ** Lyubov Reva ** Leanid Vaitsekhovich *** Oleg Illiashenko ** Oleksii Starov **

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VCC Case Study: Single-lane Bridge Problem

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  1. Summer School on Software Engineering and Verification (SSSEV) July 17-27, Moscow, Russia VCC Case Study: Single-lane Bridge Problem Formal2Normal team: • Andrey Dereza * • Anatoliy Gorbenko ** • Lyubov Reva ** • Leanid Vaitsekhovich*** • Oleg Illiashenko ** • Oleksii Starov** • _________________________________________________________ • * - Caddiesoft, Ukraine • ** - National Aerospace University “KhAI”, Ukraine • *** - Brest State Technical University, Belarus Mentors: • StephanTobies • JohnWickerson

  2. Abstract • The project is devoted to VCC case study development. • A system under study: • a real-time system that controls traffic on a single-lane bridge • The purpose of the project: • to demonstrate feasibility and usefulness of VCC tool • to compare different implementations and annotation techniques • Our approach: • to employ a stepwise (refined-based) development and verification

  3. Single-lane bridge © J.-R. Abrial. Modeling in Event-B: System and Software Engineering

  4. Single-lane bridge: System requirements

  5. Abstract model • Events • driveOut • driveInto • Invariants • n >= 0 • n <= d

  6. Step-wise development

  7. VCC implementation using Variables

  8. VCC implementation using Structure

  9. Simulation

  10. Refinement 1 • Events • m_out • m_in • i_in • i_out • Invariants • a, n, b >= 0 • a + n+ b<= MAX_COUNT • (a = 0)  (b = 0)

  11. VCC Implementation Using Structure

  12. Simulation

  13. Refinement 2 • Events • ML_out • ML_in • IN_in • IN_out • Invariants • a, n, b >= 0 • a + n+ b<= MAX_COUNT • (a = 0)  (b = 0) • il_tl xor ml_tl • …

  14. VCC implementation elements

  15. VCC implementation(next - atomic)

  16. Lessons learned • If assertion involves a variable used in a cycle above, there should be a cycle’s invariant concerns this variable => Could be implemented in VCC • Usage of structures simplifies assertions. But hierarchy of structures sophisticates proof

  17. Conclusion • Sometimes VСС requires assertions which are redundant • The complexity of the annotations depends on implementation features • To use VCC in an effective way it is necessary to work out a special coding style

  18. Any questions?

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