From Tarski to Hilbert

Se ha publicado un artículo de razonamiento aproximado en Coq sobre geometría titulado From Tarski to Hilbert.

Sus autores son Gabriel Braun y Julien Narboux (de la Universidad de Estrasburgo, Francia).

Su resumen es

In this paper, we report on the formal proof that Hilbert’s axiom system can be derived from Tarski’s system. For this purpose we mechanized the proofs of the first twelve chapters of Schwabauser, Szmielew and Tarski’s book: Metamathematische Methoden in der Geometrie. The proofs are checked formally within classical logic using the Coq proof assistant. The goal of this development is to provide clear foundations for other formalizations of geometry and implementations of decision procedures.

El trabajo se ha presentado en el ADG 2012 (Automated Deduction in Geometry 2012)

El código de las correspondientes teorías en Coq se encuentra aquí y aquí.

Mechanized metatheory for a λ λ-calculus with trust types

Se ha publicado un artículo de razonamiento formalizado en Coq titulado Mechanized metatheory for a λ λ-calculus with trust types.

Sus autores son

Su resumen es

As computer programs become increasingly complex, techniques for ensuring trustworthiness of information manipulated by them become critical. In this work, we use the Coq proof assistant to formalise a λ λ -calculus with trust types, originally formulated by Ørbæk and Palsberg. We give formal proofs of type soundness, erasure and simulation theorems and also prove decidability of the typing problem. As a result of our formalisation a certified type checker is derived.

El código de las correspondientes teorías en Coq se encuentra aquí.

La versión final del trabajo se ha publicado en el Journal of the Brazilian Computer Society.

Proving soundness of combinatorial Vickrey auctions and generating verified executable code

Se ha publicado un artículo de razonamiento formalizado en Isabelle/HOL titulado Proving soundness of combinatorial Vickrey auctions and generating verified executable code.

Sus autores son

Su resumen es

Using mechanised reasoning we prove that combinatorial Vickrey auctions are soundly specified in that they associate a unique outcome (allocation and transfers) to any valid input (bids). Having done so, we auto-generate verified executable code from the formally defined auction. This removes a source of error in implementing the auction design. We intend to use formal methods to verify new auction designs. Here, our contribution is to introduce and demonstrate the use of formal methods for auction verification in the familiar setting of a well-known auction.

El trabajo se ha desarrollado como parte del proyecto ForMaRE (Formal Mathematical Reasoning in Economics).

El código de las correspondientes teorías en Isabelle se encuentra aquí.

A computer-assisted proof of correctness of a marching cubes algorithm

Se ha publicado un artículo de razonamiento formalizado en Coq titulado A computer-assisted proof of correctness of a marching cubes algorithm.

Sus autores son Andrey N. Chernikov y Jing Xu (de la Old Dominion University, Norfolk, EEUU).

Su resumen

The Marching Cubes algorithm is a well known and widely used approach for extracting a triangulated isosurface from a three-dimensional rectilinear grid of uniformly sampled data values. The algorithm relies on a large manually constructed table which exhaustively enumerates all possible patterns in which the isosurface can intersect a cubical cell of the grid. For each pattern the table con- tains the local connectivity of the triangles. The construction of this table is labor intensive and error prone. Indeed, the original paper allowed for topological holes in the surface. This problem was later fixed by several authors, however a formal proof of correctness to our knowledge was never presented. In our opinion the most reliable approach to constructing a formal proof for this algorithm is to write a computer program which checks that all the entries in the table satisfy some sufficient condition of correctness. In this paper we present our formal proof which follows this approach, developed with the Coq proof assistant software. The script of our proof can be executed by Coq which verifies that the proof is logically correct, in the sense that its conclusions indeed logically follow from the assumptions. Coq offers a number of helpful features that automate proof development. However, Coq cannot check that the development corresponds to the problem we wish to solve, therefore, this correspondence is elaborated upon in this paper. Our complete Coq development is available online.

El trabajo se presentará en octubre en el 22nd International Meshing Roundtable.

Verifying the bridge between simplicial topology and algebra: the Eilenberg-Zilber algorithm

Se ha publicado un artículo de razonamiento formalizado en ACL2 titulado Verifying the bridge between simplicial topology and algebra: the Eilenberg-Zilber algorithm.

Sus autores son

Su resumen es

The Eilenberg–Zilber algorithm is one of the central components of the computer algebra system called Kenzo, devoted to computing in Algebraic Topology. In this article we report on a complete formal proof of the underlying Eilenberg–Zilber theorem, using the ACL2 theorem prover. As our formalization is executable, we are able to compare the results of the certified programme with those of Kenzo on some universal examples. Since the results coincide, the reliability of Kenzo is reinforced. This is a new step in our long-term project towards certified programming for Algebraic Topology.

El artículo se ha publicado en Logic Journal of the IGPL.

Los códigos de las correspondientes teorías en ACL2 se encuentran aquí.