María-José Hidalgo

Formal Proofs About Rewriting Using ACL2

We present an application of the ACL2 theorem prover to reason about rewrite systems theory. We describe the formalization and representation aspects of our work using the first-order, quantifier-free logic of ACL2 and we sketch some of the main points of the proof effort. First, we present a formalization of abstract reduction systems and then we show how this abstraction can be instantiated to establish results about term rewriting. The main theorems we mechanically proved are Newmans lemma (for abstract reductions) and Knuth–Bendix critical pair theorem (for term rewriting).

Formal verification of a generic framework to synthesize SAT-provers

We present in this paper an application of the ACL2 system to generate and reason about propositional satisfiability provers. For that purpose, we develop a framework in which we define a generic S AT-prover based on transformation rules, and we formalize this generic framework in the ACL2 logic, carrying out a formal proof of its termination, soundness, and completeness. This generic framework can be instantiated to obtain a number of verified and executable SAT-provers in ACL2, and this instantiation can be done in an automated way. Three instantiations of the generic framework are considered: semantic tableaux, sequent calculus, and Davis-Putnam-Logeman-Loveland methods.

Formal Correctness of a Quadratic Unification Algorithm

We present a case study using ACL2 to verify a nontrivial algorithm that uses efficient data structures. The algorithm receives as input two first-order terms, and it returns a most general unifier of these terms if they are unifiable, failure otherwise. The verified implementation stores terms as directed acyclic graphs by means of a pointer structure. Its time complexity is

A Formal Proof of Dickson's Lemma in ACL2

O(n^2)

Formalizing Rewriting in the ACL2 Theorem Prover

and its space complexity

Proof Pearl: a Formal Proof of Higman's Lemma in ACL2

O(n)

A Formally Verified Prover for the \mathcal{ALC\,} Description Logic

, and it can be executed in ACL2 at a speed comparable to a similar C implementation. We report the main issues encountered to achieve this formally verified implementation.

Proof pearl: a formal proof of Higman's Lemma in ACL2

Dickson’s Lemma is the main result needed to prove the termination of Buchberger’s algorithm for computing Grobner basis of polynomial ideals. In this case study, we present a formal proof of Dickson’s Lemma using the ACL2 system. Due to the limited expressiveness of the ACL2 logic, the classical non-constructive proof of this result cannot be done in ACL2. Instead, we formalize a proof where the termination argument is justified by the multiset extension of a well-founded relation.

Constructing Formally Verified Reasoners for the ALC Description Logic

We present an application of the ACL2 theorem prover to formalize and reason about rewrite systems theory. This can be seen as a first approach to apply formal methods, using ACL2, to the design of symbolic computation systems, since the notion of rewriting or simplification is ubiquitous in such systems. We concentrate here on formalization and representation aspects of abstract reduction and term rewriting systems, using the first-order, quantifier-free ACL2 logic based on Common Lisp.

Verification in ACL2 of a generic framework to synthesize SAT-provers

Higman’s lemma is an important result in infinitary combinatorics, which has been formalized in several theorem provers. In this paper we present a formalization and proof of Higman’s Lemma in the ACL2 theorem prover. Our formalization is based on a proof by Murthy and Russell, where the key termination argument is justified by the multiset relation induced by a well-founded relation. To our knowledge, this is the first mechanization of this proof.