255 research outputs found

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    A dependently typed programming language with dynamic equality

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    Dependent types offer a uniform foundation for both proof systems and programming languages. While the proof systems built with dependent types have become relatively popular, dependently typed programming languages are far from mainstream. One key issue with existing dependently typed languages is the overly conservative definitional equality that programmers are forced to use. When combined with a traditional typing workflow, these systems can be quite challenging and require a large amount of expertise to master. This thesis explores an alternative workflow and a more liberal handling of equality. Programmers are given warnings that contain the same information as the type errors that would be given by an existing system. Programmers can run these programs optimistically, and they will behave appropriately unless a direct contradiction confirming the warning is found. This is achieved by localizing equality constraints using a new form of elaboration based on bidirectional type inference. These local checks, or casts, are given a runtime behavior (similar to those of contracts and monitors). The elaborated terms have a weakened form of type soundness: they will not get stuck without an explicit counter example. The language explored in this thesis will be a Calculus of Constructions like language with recursion, type-in-type, data types with dependent indexing and pattern matching. Several meta-theoretic results will be presented. The key result is that the core language, called the cast system, "will not get stuck without a counter example"; a result called cast soundness. A proof of cast soundness is fully worked out for the fragment of the system without user defined data, and a Coq proof is available. Several other properties based on the gradual guarantees of gradual typing are also presented. In the presence of user defined data and pattern matching these properties are conjectured to hold. A prototype implementation of this work is available

    Meta-ontology fault detection

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    Ontology engineering is the field, within knowledge representation, concerned with using logic-based formalisms to represent knowledge, typically moderately sized knowledge bases called ontologies. How to best develop, use and maintain these ontologies has produced relatively large bodies of both formal, theoretical and methodological research. One subfield of ontology engineering is ontology debugging, and is concerned with preventing, detecting and repairing errors (or more generally pitfalls, bad practices or faults) in ontologies. Due to the logical nature of ontologies and, in particular, entailment, these faults are often both hard to prevent and detect and have far reaching consequences. This makes ontology debugging one of the principal challenges to more widespread adoption of ontologies in applications. Moreover, another important subfield in ontology engineering is that of ontology alignment: combining multiple ontologies to produce more powerful results than the simple sum of the parts. Ontology alignment further increases the issues, difficulties and challenges of ontology debugging by introducing, propagating and exacerbating faults in ontologies. A relevant aspect of the field of ontology debugging is that, due to the challenges and difficulties, research within it is usually notably constrained in its scope, focusing on particular aspects of the problem or on the application to only certain subdomains or under specific methodologies. Similarly, the approaches are often ad hoc and only related to other approaches at a conceptual level. There are no well established and widely used formalisms, definitions or benchmarks that form a foundation of the field of ontology debugging. In this thesis, I tackle the problem of ontology debugging from a more abstract than usual point of view, looking at existing literature in the field and attempting to extract common ideas and specially focussing on formulating them in a common language and under a common approach. Meta-ontology fault detection is a framework for detecting faults in ontologies that utilizes semantic fault patterns to express schematic entailments that typically indicate faults in a systematic way. The formalism that I developed to represent these patterns is called existential second-order query logic (abbreviated as ESQ logic). I further reformulated a large proportion of the ideas present in some of the existing research pieces into this framework and as patterns in ESQ logic, providing a pattern catalogue. Most of the work during my PhD has been spent in designing and implementing an algorithm to effectively automatically detect arbitrary ESQ patterns in arbitrary ontologies. The result is what we call minimal commitment resolution for ESQ logic, an extension of first-order resolution, drawing on important ideas from higher-order unification and implementing a novel approach to unification problems using dependency graphs. I have proven important theoretical properties about this algorithm such as its soundness, its termination (in a certain sense and under certain conditions) and its fairness or completeness in the enumeration of infinite spaces of solutions. Moreover, I have produced an implementation of minimal commitment resolution for ESQ logic in Haskell that has passed all unit tests and produces non-trivial results on small examples. However, attempts to apply this algorithm to examples of a more realistic size have proven unsuccessful, with computation times that exceed our tolerance levels. In this thesis, I have provided both details of the challenges faced in this regard, as well as other successful forms of qualitative evaluation of the meta-ontology fault detection approach, and discussions about both what I believe are the main causes of the computational feasibility problems, ideas on how to overcome them, and also ideas on other directions of future work that could use the results in the thesis to contribute to the production of foundational formalisms, ideas and approaches to ontology debugging that can properly combine existing constrained research. It is unclear to me whether minimal commitment resolution for ESQ logic can, in its current shape, be implemented efficiently or not, but I believe that, at the very least, the theoretical and conceptual underpinnings that I have presented in this thesis will be useful to produce more foundational results in the field

    On Causal Equivalence by Tracing in String Rewriting

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    We introduce proof terms for string rewrite systems and, using these, show that various notions of equivalence on reductions known from the literature can be viewed as different perspectives on the notion of causal equivalence. In particular, we show that permutation equivalence classes (as known from the lambda-calculus and term rewriting) are uniquely represented both by trace graphs (known from physics as causal graphs) and by so-called greedy multistep reductions (as known from algebra). We present effective maps from the former to the latter, topological multi-sorting TM, and vice versa, the proof term algebra [[ ]].Comment: In Proceedings TERMGRAPH 2022, arXiv:2303.1421

    Le postcolonialisme et le postmodernisme à l’épreuve de la contemporanéité

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    -Postcolonialisme et féminisme -Postcolonialisme et postmodernisme face aux nouveaux profils littéraires -Postcolonialisme et postmodernisme pour une étude comparée -Postcolonialisme au prisme des Lettres et Sciences Humaines et Sociale

    Committed to the Fragment: Feminist Literature and the Promise of Wellness

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    “I have never been able to blind myself” to the cruelty of a world that “destroys its own young in passing…out of not noticing or caring about the destruction,” Audre Lorde tells us in her 1980 “mythobiography” Zami: A New Spelling of My Name. This quality, Lorde says, “according to one popular definition of mental health, makes me mentally unhealthy.” In rejecting psychological self-possession as a sign of wellness, this passage also rejects it as one of sovereignty’s conditions. At the time of Lorde’s writing, this version of sovereignty already dominated the landscape of therapeutic culture in the United States, and would become only more staggeringly pervasive and profitable in the years to come. In our therapeutic age, to establish oneself as one of neoliberalism’s winners requires performing a healthist form of psychic well-being -- one that overlaps with Enlightenment ideals of autonomy and rationality. This dissertation explores how literary genres and forms reject psychic well-being as a privilege of bourgeois liberalism and a panacea for heteronormativity’s discontents. These texts are what I read as “feminist literature.” They turn to emergent genres and forms to refigure wellness as a generative relation to difference – a relation that, in Lorde’s Black feminist framework, is always bound up with the pain of others. Specifically, I read Lorde’s genre-bending memoir The Cancer Journals; the post-2016 genre of self-care comedy; and autotheory about the Diagnostic and Statistical Manual of Mental Disorders (DSM) as examining how sexist, racist, and ableist ideals of wellness have placed fraught and contradictory demands on the feminist subject. I argue that these texts represent the writing process itself as crucial for addressing this question: a site for revising the literary conventions that evince a liberal subject’s mind at work, as well as for interrogating how medicalized norms structure writing cultures, academic and otherwise. Writing appears across a range of genres – memoir; fiction; cultural criticism; and autotheory – as a practice that identifies illness, wellness, and aesthetics as pressingly concerned with gender and power

    DeepSec: Deciding Equivalence Properties for Security Protocols -- Improved theory and practice

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    Automated verification has become an essential part in the security evaluation of cryptographic protocols. In this context privacy-type properties are often modelled by indistinguishability statements, expressed as behavioural equivalences in a process calculus. In this paper we contribute both to the theory and practice of this verification problem. We establish new complexity results for static equivalence, trace equivalence and labelled bisimilarity and provide a decision procedure for these equivalences in the case of a bounded number of protocol sessions. Our procedure is the first to decide trace equivalence and labelled bisimilarity exactly for a large variety of cryptographic primitives -- those that can be represented by a subterm convergent destructor rewrite system. We also implemented the procedure in a new tool, DeepSec. We showed through extensive experiments that it is significantly more efficient than other similar tools, while at the same time raises the scope of the protocols that can be analysed.Comment: 104 page

    Tools and Algorithms for the Construction and Analysis of Systems

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    This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems
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