Concepts de base
This paper presents an inductive inference system that combines automated and explicit-induction theorem proving techniques to prove validity of formulas in the initial algebra of an order-sorted equational theory. The system uses advanced equational reasoning techniques, including equationally defined equality predicates, narrowing, constructor variant unification, variant satisfiability, order-sorted congruence closure, contextual rewriting, and ordered rewriting, all working modulo axioms.
Résumé
The paper presents an inductive inference system for proving validity of formulas in the initial algebra TE of an order-sorted equational theory E. The system has 20 inference rules, with 11 of them being fully automated simplification rules and the remaining 9 requiring user interaction. This combination of automated and explicit-induction techniques aims to automate a substantial fraction of the proof effort.
The key techniques used in the inference system include:
- Equationally defined equality predicates to reduce first-order logic satisfaction of quantifier-free formulas in the initial algebra to purely equational reasoning.
- Narrowing, including constrained narrowing, to symbolically evaluate terms with the given equations.
- Constructor variant unification and variant satisfiability to handle existential quantification.
- Order-sorted congruence closure, contextual rewriting, and ordered rewriting to simplify formulas.
All these techniques work modulo axioms B, which can be any combination of associativity, commutativity, and identity axioms. The paper also discusses the theoretical foundations of the inference system, including its soundness, and provides numerous examples illustrating the use of the different inference rules.