Typeful Normalization by Evaluation

We present the first typeful implementation of Normalization by Evaluation for the simply typed lambda-calculus with sums and control operators: we guarantee type preservation and eta-long (modulo commuting conversions), beta-normal forms using only Generalized Algebraic Data Types in a general-purpose programming language, here OCaml; and we account for sums and control operators with Continuation-Passing Style. First, we implement the standard NbE algorithm for the implicational fragment in a typeful way that is correct by construction. We then derive its call-by-value continuation-passing counterpart, that maps a lambda-term with sums and call/cc into a CPS term in normal form, which we express in a typed dedicated syntax. Beyond showcasing the expressive power of GADTs, we emphasize that type inference gives a smooth way to re-derive the encodings of the syntax and typing of normal forms in Continuation-Passing Style

Asynchronous Probabilistic Couplings in Higher-Order Separation Logic

Probabilistic couplings are the foundation for many probabilistic relational program logics and arise when relating random sampling statements across two programs. In relational program logics, this manifests as dedicated coupling rules that, e.g., say we may reason as if two sampling statements return the same value. However, this approach fundamentally requires aligning or "synchronizing" the sampling statements of the two programs which is not always possible. In this paper, we develop Clutch, a higher-order probabilistic relational separation logic that addresses this issue by supporting asynchronous probabilistic couplings. We use Clutch to develop a logical step-indexed logical relational to reason about contextual refinement and equivalence of higher-order programs written in a rich language with higher-order local state and impredicative polymorphism. Finally, we demonstrate the usefulness of our approach on a number of case studies. All the results that appear in the paper have been formalized in the Coq proof assistant using the Coquelicot library and the Iris separation logic framework

A Completeness Theorem for Probabilistic Regular Expressions

We introduce Probabilistic Regular Expressions (PRE), a probabilistic analogue of regular expressions denoting probabilistic languages in which every word is assigned a probability of being generated. We present and prove the completeness of an inference system for reasoning about probabilistic language equivalence of PRE based on Salomaa's axiomatisation of Kleene Algebra

Accounting historians notebook, 2011, Vol. 34, no. 1 (April) [whole issue]

Copyright held by: Academy of Accounting Historian

Computing Knowledge in Equational Extensions of Subterm Convergent Theories

International audienceWe study decision procedures for two knowledge problems critical to the verification of security protocols, namely the intruder deduction and the static equivalence problems. These problems can be related to particular forms of context matching and context unification. Both problems are defined with respect to an equational theory and are known to be decidable when the equational theory is given by a subterm convergent term rewrite system. In this work we extend this to consider a subterm convergent term rewrite system defined modulo an equational theory, like Commutativity. We present two pairs of solutions for these important problems. The first solves the deduction and static equivalence problems in systems modulo shallow theories such as Commutativity. The second provides a general procedure that solves the deduction and static equivalence problems in subterm convergent systems modulo syntactic permutative theories, provided a finite measure is ensured. Several examples of such theories are also given

'An expressive kind of history' : Anti-Jacobite prints and the 1745 rebellion

Following the removal of James II from the thrones of England, Scotland and Ireland in 1689, the last meaningful attempt to restore the Stuart dynasty was made in 1745, when Charles Stuart, grandson of James II, landed in Scotland, his makeshift army managing to get within one hundred and twenty miles of London. This thesis explores the printed visual imagery expressing the Hanoverian viewpoint on the momentous events of the mid-1740s. This imagery addressed the broad religious, political, social and economic debates of the period, seeking to discredit the Jacobite agenda, the leader of the rebellion and its supporters. Graphic satire proved to be an especially important medium for presenting the arguments in favour of George II, as part of a wider debate carried on in the press, pamphlets and elsewhere. The Hanoverian cause was bolstered by the communication of ideas in the form of these images, incorporating a sophisticated array of visual languages and strategies, in addition to engaging extensively with other media. Whilst William Hogarth may have been the eighteenth-century master of imagery involving a wealth of graphic detail and multiple layers of inter-related meaning in his prints, those lesser artists involved in producing antiJacobite imagery were also capable of employing such tactics with skill. This thesis provides an analytical survey of the anti-Jacobite imagery produced at the time of the 1745 rebellion which has, hitherto, been given little attention. My aim is to establish the full extent of the pro-Hanoverian printed imagery of the years 1743-7 and to evaluate its content, market and influence. Of particular concern are the strategies used to address a diverse audience with varying degrees of visual and textual literacy skills and the extent to which anti-Jacobite prints may be classed as ‘propaganda’

The challenges of translating the women's group Participatory Learning and Action Cycle from multiple low-income countries to the UK NHS context, using nutrition in infants of Bangladeshi origin in Tower Hamlets as an exemplar.

Background There is a need for cost-effective and adaptable health interventions to address complex issues within the UK National Health Service (NHS). Reverse innovation in public health is the process of adapting health interventions developed in low-income countries (LICs) and implementing them in high-income contexts (HICs) (1). This process is gaining traction in global health as a means of offers knowledge sharing between the global south and the global north. The adaptation of interventions from one context to another is ubiquitous and necessary, but the process is often unrecorded. There is a tension between fidelity to the intervention and adaptation to the specific needs of the target context and a heterogeneous population. In the UK, ethnic minority groups in particular experience disproportionate levels of obesity, type 2 diabetes, cardiovascular disease and micronutrient deficiencies compared with the majority White European-origin population (2), and current NHS services are unable to address the increasing rates of nutrition-related ill-health in these populations. Furthermore, there are inconsistencies in the effectiveness of NHS interventions in minority ethnic groups and there is a risk of intervention generated inequalities. Adapting interventions that have been subject to reverse innovation could increase intervention effectiveness in their new context. The aim of this thesis is to present a framework that supports the theoretical adaptation of one such intervention, the women’s group Participatory Learning and Action cycle (PLA cycle) (3) using the Nurture Early for Infant Nutrition (NEON) study (4) in the Bangladeshi population of Tower Hamlets as an exemplar. The framework is intended for multiple policy, practice and research benefits. Failing to follow a framework for implementation could lead to an unsuccessful intervention (5). Methods This thesis employed a qualitative research design across two studies: 1. The principles of how the women’s group PLA cycle was adapted in practice were captured through Study 1. This study explored the process of adaptation to the women’s group PLA cycle across the original seven cluster randomised controlled trials (RCTs) in Bangladesh, India, Nepal and Malawi through 14 key informant interviews. 2. Study 2 determined the specific contextual adaptations that could address the acceptability and feasibility to the women’s group PLA cycle through focus group discussions (FGDs) with individuals of Bangladeshi-origin from Tower Hamlets. All data were subject to the Braun and Clarke (2006) guidelines to thematic analysis (6). Results The key informant interviews generated data that resulted in an outline of a generic theoretical adaptation framework. The framework includes components requiring fidelity and those requiring subtle adaptations. The four-stage framework detailed a preparation phase, the process of adaptations and highlighted a specific set of micro-adaptations that can be adjusted to emulate local context. The FGDs aimed to address the micro-adaptations that were suggested by the key informants. They showed a paradoxical relationship between the participants’ Bangladeshi heritage and their lived environment. There were specific differences between individuals who had been in the country for less than three years, those that had been in the country for more than three years, and those that had been born in the UK but whose parents were from Bangladesh. Discussion The women’s group PLA theoretical adaptation framework is the first attempt to create a formal adaptation structure for the PLA cycle which is also relevant to other participatory intervention paradigms. The framework was developed in the context of a wider study about reverse innovation of the women’s group PLA cycle model but would also be relevant to any situation where a participatory intervention is being adapted. Relatively few studies have previously considered the macro policy and political context as a influencers on adaptation processes for health interventions, although this is well characterised in implementation literature (7). Recognising the inherent differences within the Bangladeshi population of Tower Hamlets could allow the women’s group PLA cycle to be adapted appropriately by the NEON study. I believe it is important to adjust the micro-adaptations to encompass both areas of the population’s identity - heritage and environment. This has implications for other interventions that are looking to culturally adapt their interventions for minority populations in the UK. Conclusion The theoretical adaptation framework for the women’s group PLA cycle is new to the innovation literature, because they outline areas to consider when an intervention developed in a LIC is undergoing reverse innovation. Strength lies in the homogeneity of experience of the key informants, meaning that data had less ‘noise’ in terms of the actual intervention itself. This thesis has constructed a theoretical framework that could potentially assist other researchers with the adaptation of the model into their HIC context

Stochastic Invariants for Probabilistic Termination

Termination is one of the basic liveness properties, and we study the termination problem for probabilistic programs with real-valued variables. Previous works focused on the qualitative problem that asks whether an input program terminates with probability~1 (almost-sure termination). A powerful approach for this qualitative problem is the notion of ranking supermartingales with respect to a given set of invariants. The quantitative problem (probabilistic termination) asks for bounds on the termination probability. A fundamental and conceptual drawback of the existing approaches to address probabilistic termination is that even though the supermartingales consider the probabilistic behavior of the programs, the invariants are obtained completely ignoring the probabilistic aspect. In this work we address the probabilistic termination problem for linear-arithmetic probabilistic programs with nondeterminism. We define the notion of {\em stochastic invariants}, which are constraints along with a probability bound that the constraints hold. We introduce a concept of {\em repulsing supermartingales}. First, we show that repulsing supermartingales can be used to obtain bounds on the probability of the stochastic invariants. Second, we show the effectiveness of repulsing supermartingales in the following three ways: (1)~With a combination of ranking and repulsing supermartingales we can compute lower bounds on the probability of termination; (2)~repulsing supermartingales provide witnesses for refutation of almost-sure termination; and (3)~with a combination of ranking and repulsing supermartingales we can establish persistence properties of probabilistic programs. We also present results on related computational problems and an experimental evaluation of our approach on academic examples.Comment: Full version of a paper published at POPL 2017. 20 page

The Grand Tour Correspondence of two Eighteenth-Century Clergymen from the Diocese of Waterford & Lismore

The correspondences of Dr Richard Pococke and his cousin Jeremiah Milles, tracing in detail their eighteenth century travels through Europe and the Orient, have been previously overlooked in historiographical terms. Rachel Finnegan’s article brings these letters to life, charting the personal and professional lives of these two clergymen, revealing the disparate range of subjects dealt with in their correspondences and thereby highlighting the potential value of these documents as historical sources