Lean4 proof that SSOT requires definition-time hooks and introspection
I formalized the Single Source of Truth (SSOT) principle in Lean 4 (~2.1k LOC, zero sorry) and proved two core results: Structural SSOT is achievable only when a language provides definition-time hooks and runtime introspection. Macros/codegen (before definition) and reflection (after definition) are insufficient. These requirements are derived, not chosen: because structural facts are fixed at definition, derivation must occur at definition time and be introspectable to verify DOF = 1. Would appreciate review, critique, or independent checking of the Lean scripts.
In plain words
This Lean 4 formalization demonstrates that achieving Single Source of Truth for structural data requires programming language support for definition-time hooks and runtime introspection. The work proves macros and reflection alone are insufficient, using approximately 2,100 lines of code with no incomplete proofs. It is designed for language designers, formal methods researchers, and developers interested in how software architecture principles can be mathematically verified. The key contribution is deriving these requirements from first principles rather than assuming them.
written from the facts on this page · September 2026
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