Generating Verified LLVM from Isabelle/HOL

We present a framework to generate verified LLVM programs from Isabelle/HOL. It is based on a code generator that generates LLVM text from a simplified fragment of LLVM, shallowly embedded into Isabelle/HOL. On top, we have developed a separation logic, a verification condition generator, and an LLVM backend to the Isabelle Refinement Framework. As case studies, we have produced verified LLVM implementations of binary search and the Knuth-Morris-Pratt string search algorithm. These are one order of magnitude faster than the Standard-ML implementations produced with the original Refinement Framework, and on par with unverified C implementations. Adoption of the original correctness proofs to the new LLVM backend was straightforward. The trusted code base of our approach is the shallow embedding of the LLVM fragment and the code generator, which is a pretty printer combined with some straightforward compilation steps

Formally Verified SAT-Based AI Planning

We present an executable formally verified SAT encoding of classical AI planning. We use the theorem prover Isabelle/HOL to perform the verification. We experimentally test the verified encoding and show that it can be used for reasonably sized standard planning benchmarks. We also use it as a reference to test a state-of-the-art SAT-based planner, showing that it sometimes falsely claims that problems have no solutions of certain lengths

Formalizing the Metatheory of Logical Calculi and Automatic Provers in Isabelle/HOL (Invited Talk)

International audienceIsaFoL (Isabelle Formalization of Logic) is an undertaking that aims at developing formal theories about logics, proof systems, and automatic provers, using Isabelle/HOL. At the heart of the project is the conviction that proof assistants have become mature enough to actually help researchers in automated reasoning when they develop new calculi and tools. In this paper, I describe and reflect on three verification subprojects to which I contributed: a first-order resolution prover, an imperative SAT solver, and generalized term orders for λ-free higher-order logic

Tools and Algorithms for the Construction and Analysis of Systems

This open access two-volume set constitutes the proceedings of the 27th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2021, which was held during March 27 – April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The total of 41 full papers presented in the proceedings was carefully reviewed and selected from 141 submissions. The volume also contains 7 tool papers; 6 Tool Demo papers, 9 SV-Comp Competition Papers. The papers are organized in topical sections as follows: Part I: Game Theory; SMT Verification; Probabilities; Timed Systems; Neural Networks; Analysis of Network Communication. Part II: Verification Techniques (not SMT); Case Studies; Proof Generation/Validation; Tool Papers; Tool Demo Papers; SV-Comp Tool Competition Papers

A verified prover based on ordered resolution

International audienceThe superposition calculus, which underlies first-order theorem provers such as E, SPASS, and Vampire, combines ordered resolution and equality reasoning. As a step towards verifying modern provers, we specify, using Isabelle/HOL, a purely functional first-order ordered resolution prover and establish its soundness and refutational completeness. Methodologically, we apply stepwise refinement to obtain, from an abstract nondeterministic specification, a verified de-terministic program, written in a subset of Isabelle/HOL from which we extract purely functional Standard ML code that constitutes a semidecision procedure for first-order logic

Tools and Algorithms for the Construction and Analysis of Systems

This open access two-volume set constitutes the proceedings of the 27th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2021, which was held during March 27 – April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The total of 41 full papers presented in the proceedings was carefully reviewed and selected from 141 submissions. The volume also contains 7 tool papers; 6 Tool Demo papers, 9 SV-Comp Competition Papers. The papers are organized in topical sections as follows: Part I: Game Theory; SMT Verification; Probabilities; Timed Systems; Neural Networks; Analysis of Network Communication. Part II: Verification Techniques (not SMT); Case Studies; Proof Generation/Validation; Tool Papers; Tool Demo Papers; SV-Comp Tool Competition Papers

Pandemocracy in Europe

This open access book explains why a democratic reckoning will start when European societies win the fight against COVID-19. Have democracies successfully mastered the challenges of the pandemic? How has the coronavirus impacted democratic principles, processes and values? At the heels of the worst public health crisis in living memory, this book shines an unforgiving light on the side-lining of parliaments, the ruling by governmental decrees and the disenfranchisement of the people in the name of fighting COVID-19. Pandemocracy in Europe situates the dramatic impact of COVID-19, and the fight against the virus, on Europe's democracies. Throughout its 17 contributions the book sets the theoretical stage and answers the democratic questions engaged by health emergencies. Seven national case studies – UK, Germany, Italy, Sweden, Hungary, Switzerland, and France – show, each time with a pronounced focus on a particular element of democracy, how different states reacted to the pandemic. The book also shifts the analytical gaze beyond the nation state towards international settings, looking at the effects on the European Union and considering the impact on populist movements. Bridging disciplines and uniting a stellar cast of scholars on democracy, rule of law and constitutionalism, the book provides contours and nuances to a year of debates in political science, international relations and law on the impact of the virus on democracies. In times of uncertainty, Pandemocracy in Europe provides analysis and answers to the democratic challenges of the coronavirus. The open access edition of this book is available under a CC BY-NC-ND 4.0 licence on www.bloomsburycollections.com

Pandemocracy in Europe

This open access book explains why a democratic reckoning will start when European societies win the fight against COVID-19. Have democracies successfully mastered the challenges of the pandemic? How has the coronavirus impacted democratic principles, processes and values? At the heels of the worst public health crisis in living memory, this book shines an unforgiving light on the side-lining of parliaments, the ruling by governmental decrees and the disenfranchisement of the people in the name of fighting COVID-19. Pandemocracy in Europe situates the dramatic impact of COVID-19, and the fight against the virus, on Europe's democracies. Throughout its 17 contributions the book sets the theoretical stage and answers the democratic questions engaged by health emergencies. Seven national case studies – UK, Germany, Italy, Sweden, Hungary, Switzerland, and France – show, each time with a pronounced focus on a particular element of democracy, how different states reacted to the pandemic. The book also shifts the analytical gaze beyond the nation state towards international settings, looking at the effects on the European Union and considering the impact on populist movements. Bridging disciplines and uniting a stellar cast of scholars on democracy, rule of law and constitutionalism, the book provides contours and nuances to a year of debates in political science, international relations and law on the impact of the virus on democracies. In times of uncertainty, Pandemocracy in Europe provides analysis and answers to the democratic challenges of the coronavirus. The open access edition of this book is available under a CC BY-NC-ND 4.0 licence on www.bloomsburycollections.com