TLA+ validation of Chord
summary
Mechanized TLA+ model and Isabelle proofs validate Chord maintenance: the model, fully mechanized in Isabelle-TLA with a Principals theory in Isabelle‑HOL, proves that when no joins/fails occur the first element of each successor list converges to the sucNode function and prdc fields converge to prevNode. Core Pamela Zave invariants hold, propagation completes after at most |M| steps, and crucially stabilization liveness holds under weak fairness (not strong fairness).
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chapters (13)
- 0:00Introduction to Chord validation
- 1:14Chord maintenance protocol overview
- 2:40Focus on stabilization liveness property
- 3:21Node state model in TLA+
- 4:33Maintenance protocol transitions
- 6:26Principle nodes and ring properties
- 9:07Key theorems on principles and functions
- 10:56Back propagation of predicates
- 12:12Formal verification goals
- 13:17Stabilization proof phases
- 15:16Propagation mechanism illustration
- 17:06Isabelle-TLA mechanization details
- 19:41Conclusion and results summary
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