Abstract

Recent versions of the proof assistant Isabelle have acquired a “local theory” concept that integrates a variety of mechanisms for structured specifications into a common framework. We explicitly separate a local theory “target” from its “body”, i.e. a fixed axiomatic specification (parameters and assumptions) vs. arbitrary definitional extensions (conclusions) depending on it. Body elements may be added incrementally, and admit local polymorphism according to Hindley-Milner. The foundations of our local theories rest firmly on existing Isabelle/Isar principles, without having to invent new logics or module calculi. Particular target contexts and body elements may be implemented within the generic infrastructure. This results in a large combinatorial space of specification idioms available to the end-user. Here we introduce targets for Isabelle locales, type-classes, and class instantiations. The available selection of body elements covers primitive definitions and theorems, inductive predicates and sets, and recursive functions. Porting such existing definitional packages is reasonably simple, and enables to re-use sophisticated tools in a variety of target contexts without further ado. For example, a recursive function may be defined depending on locale parameters and assumptions, or an inductive predicate definition may provide the witness in a type-class instantiation.

Citations