A Uniform Substitution Calculus for Differential Dynamic Logic

Abstract

AbstractThis paper introduces a new proof calculus for differential dynamic logic (\(\mathsf {d}\mathcal {L}\)) that is entirely based on uniform substitution, a proof rule that substitutes a formula for a predicate symbol everywhere. Uniform substitutions make it possible to rely on axioms rather than axiom schemata, substantially simplifying implementations. Instead of subtle schema variables and soundness-critical side conditions on the occurrence patterns of variables, the resulting calculus adopts only a finite number of ordinary \(\mathsf {d}\mathcal {L}\) formulas as axioms. The static semantics of differential dynamic logic is captured exclusively in uniform substitutions and bound variable renamings as opposed to being spread in delicate ways across the prover implementation. In addition to sound uniform substitutions, this paper introduces differential forms for differential dynamic logic that make it possible to internalize differential invariants, differential substitutions, and derivations as first-class axioms in \(\mathsf {d}\mathcal {L}\).KeywordsFree VariableFunction SymbolPredicate SymbolStatic SemanticAxiom SchemaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.