23 research outputs found

    Verified programming with explicit coercions

    Get PDF
    Type systems have proved to be a powerful means of specifying and proving important program invariants. In dependently typed programming languages types can depend on values and hence express arbitrarily complicated propositions and their machine checkable proofs. The type-based approach to program specification allows for the programmer to not only transcribe their intentions, but arranges for their direct involvement in the proving process, thus aiding the machine in its attempt to satisfy difficult obligations. In this thesis we develop a series of patterns for programming in a correct-by-construction style making use of constraints and coercions to prove properties within a dependently typed host. This allows for the development of a verified, kernel which can be built upon using the host system features. In particular this should allow for the development of “tactics” or semiautomated solvers invoked when coercing types all within a single language. The efficacy of this approach is given by the development of a system of expressions indexed by their, exposing a case analysis feature serving to generate value constraints. These constraints are directly reflected into the host allowing for their involvement in the type-checking process. A motivating use case of this design shows how a term’s semantic index information admits an exact, formalized cost analysis amenable to reasoning within the host. Finally we show how such a system is used to identify unreachable dead-code, trivially admitting the design and verification of an SSA style compiler with this optimization. We think such a design of explicitly proving the local correctness of type-transformations in the presence of accumulated constraints can form the basis of a flexible language in concert with a variety of trusted solver

    Modular Type-Safety Proofs in Agda

    No full text
    Methods for reusing code are widespread and well researched, but methods for reusing proofs are still emerging. We consider the use of dependent types for this purpose, introducing a modular approach for composing mechanized proofs. We show that common techniques for abstracting algorithms over data structures naturally translate to abstractions over proofs. We introduce a language composed of a series of smaller language components, each defined as functors, and tie them together by taking the fixed point of their sum [Malcom, 1990]. We then give proofs of type preservation for each language component and show how to compose these proofs into a proof for the entire language, again by taking the fixed point of a sum of functors

    Solutions for Recovering and Sustaining the Bounty of the Ocean: Combining Fishery Reforms, Rights-Based Fisheries Management, and Marine Reserves

    No full text
    This manuscript is based on a keynote lecture given by Jane Lubchenco at One Planet, One Ocean: The 2nd International Ocean Research Conference, Barcelona, Spain, November 17–21, 2014. Food security, economic opportunities, and other benefits provided by a healthy ocean are in jeopardy because of years of overexploitation of many fisheries, and the challenges will intensify in many locales as climate and the environment continue to change. The good news is that solutions are gaining traction. Mandates to end overfishing that use scientifically determined catch limits and rights-based approaches to fishery management have produced impressive results in ending overfishing and recovering depleted stocks. Similarly, spatial protections, such as fully protected marine reserves, are increasing the diversity, size, and abundance of species within reserves; some of that bounty reaches fished areas outside of them. We review the effects of combining catch limits, rights-based fisheries approaches, and establishment of marine reserves and discuss additional advantages of these combined solutions in securing sustainable and profitable fisheries, community goals, and healthy ecosystems. This paper highlights the contribution of emerging science-based solutions and the steps needed to replicate and scale these successes. Triple-wins for the environment, the economy, and society can be achieved through integrated fisheries management and protection as conscious steps toward reversing the current degradation of our ocean’s living resources

    Solutions for Recovering and Sustaining the Bounty of the Ocean: Combining Fishery Reforms, Rights-Based Fisheries Management, and Marine Reserves

    No full text
    This manuscript is based on a keynote lecture given by Jane Lubchenco at One Planet, One Ocean: The 2nd International Ocean Research Conference, Barcelona, Spain, November 17–21, 2014. Food security, economic opportunities, and other benefits provided by a healthy ocean are in jeopardy because of years of overexploitation of many fisheries, and the challenges will intensify in many locales as climate and the environment continue to change. The good news is that solutions are gaining traction. Mandates to end overfishing that use scientifically determined catch limits and rights-based approaches to fishery management have produced impressive results in ending overfishing and recovering depleted stocks. Similarly, spatial protections, such as fully protected marine reserves, are increasing the diversity, size, and abundance of species within reserves; some of that bounty reaches fished areas outside of them. We review the effects of combining catch limits, rights-based fisheries approaches, and establishment of marine reserves and discuss additional advantages of these combined solutions in securing sustainable and profitable fisheries, community goals, and healthy ecosystems. This paper highlights the contribution of emerging science-based solutions and the steps needed to replicate and scale these successes. Triple-wins for the environment, the economy, and society can be achieved through integrated fisheries management and protection as conscious steps toward reversing the current degradation of our ocean’s living resources

    Proof-Carrying Plans: a Resource Logic for AI Planning

    No full text
    Recent trends in AI verification and Explainable AI have raised the question of whether AI planning techniques can be verified. In this paper, we present a novel resource logic, the Proof Carrying Plans (PCP) logic that can be used to verify plans produced by AI planners. The PCP logic takes inspiration from existing resource logics (such as Linear logic and Separation logic) as well as Hoare logic when it comes to modelling states and resource-aware plan execution. It also capitalises on the Curry-Howard approach to logics, in its treatment of plans as functions and plan pre- and post-conditions as types. This paper presents two main results. From the theoretical perspective, we show that the PCP logic is sound relative to the standard possible world semantics used in AI planning. From the practical perspective, we present a complete Agda formalisation of the PCP logic and of its soundness proof. Moreover, we showcase the Curry-Howard, or functional, value of this implementation by supplementing it with the library that parses AI plans into Agda's proofs automatically. We provide evaluation of this library and the resulting Agda functions.Comment: PPDP 2020, 13 pages, 9 figure

    Stripping away ion hydration shells in electrical double-layer formation: Water networks matter

    No full text
    International audienceThe double layer at the solid/electrolyte interface is a key concept in electrochemistry. Here, we present an experimental study combined with simulations, which provides a molecular picture of the double-layer formation under applied voltage. By THz spectroscopy we are able to follow the stripping away of the cation/anion hydration shells for an NaCl electrolyte at the Au surface when decreasing/increasing the bias potential. While Na + is attracted toward the electrode at the smallest applied negative potentials, stripping of the Cl − hydration shell is observed only at higher potential values. These phenomena are directly measured by THz spectroscopy with ultrabright synchrotron light as a source and rationalized by accompanying molecular dynamics simulations and electronic-structure calculations

    Stripping off of the Hydration Shells in the Double Layer Formation: Water Networks Matter

    No full text
    The double layer at the solid/electrolyte interface is a key concept in electrochemistry. Here, we present an experimental study combined with simulations, which provides a molecular picture of the double-layer formation in operando processes. By THz spectroscopy we are able to follow the stripping off of the cation/anion hydration shells for a NaCl electrolyte at the Au surface when decreasing/increasing the bias potential. While Na+ is attracted toward the electrode already at the smallest applied negative potentials, stripping-off of the Cl- hydration shell is observed only at higher potential values. These phenomena are directly measured by in operando THz spectroscopy with ultra-bright synchrotron light as a source and rationalized by accompanying molecular-dynamics simulations and electronic-structure calculations. </div
    corecore