Horn Binary Serialization Analysis

A bit layout is a sequence of fields of certain bit lengths that specifies how to interpret a serial stream, e.g., the MP3 audio format. A layout with variable length fields needs to include meta-information to help the parser interpret unambiguously the rest of the stream; e.g. a field providing the length of a following variable length field. If no such information is available, then the layout is ambiguous. I present a linear-time algorithm to determine whether a layout is ambiguous or not by modelling the behaviour of a serial parser reading the stream as forward chaining reasoning on a collection of Horn clauses.Comment: In Proceedings HCVS2016, arXiv:1607.0403

Inferring Termination Conditions for Logic Programs using Backwards Analysis

This paper focuses on the inference of modes for which a logic program is guaranteed to terminate. This generalises traditional termination analysis where an analyser tries to verify termination for a specified mode. Our contribution is a methodology in which components of traditional termination analysis are combined with backwards analysis to obtain an analyser for termination inference. We identify a condition on the components of the analyser which guarantees that termination inference will infer all modes which can be checked to terminate. The application of this methodology to enhance a traditional termination analyser to perform also termination inference is demonstrated

Control Flow Analysis for SF Combinator Calculus

Programs that transform other programs often require access to the internal structure of the program to be transformed. This is at odds with the usual extensional view of functional programming, as embodied by the lambda calculus and SK combinator calculus. The recently-developed SF combinator calculus offers an alternative, intensional model of computation that may serve as a foundation for developing principled languages in which to express intensional computation, including program transformation. Until now there have been no static analyses for reasoning about or verifying programs written in SF-calculus. We take the first step towards remedying this by developing a formulation of the popular control flow analysis 0CFA for SK-calculus and extending it to support SF-calculus. We prove its correctness and demonstrate that the analysis is invariant under the usual translation from SK-calculus into SF-calculus.Comment: In Proceedings VPT 2015, arXiv:1512.0221

Generic Modal Cut Elimination Applied to Conditional Logics

We develop a general criterion for cut elimination in sequent calculi for propositional modal logics, which rests on absorption of cut, contraction, weakening and inversion by the purely modal part of the rule system. Our criterion applies also to a wide variety of logics outside the realm of normal modal logic. We give extensive example instantiations of our framework to various conditional logics. For these, we obtain fully internalised calculi which are substantially simpler than those known in the literature, along with leaner proofs of cut elimination and complexity. In one case, conditional logic with modus ponens and conditional excluded middle, cut elimination and complexity were explicitly stated as open in the literature

Selective feeding centres in refugee settings: evaluation framework protocol

Selective feeding programs are centres for the treatment of persons suffering from acute malnutrition. Unlike chronic malnutrition, acute malnutrition reflects recent problems. In a crisis situation, wasting is preferred above other indicators because it is sensitive to rapid change, indicates present change, can be used to monitor the impact of interventions and is a good predictor of immediate mortality risk. This paper reviews the current approach being used in the field to evaluate the effectiveness of feeding programs. There is no comprehensive evaluation framework in place to assess the impact of feeding programs on mortality due to malnutrition. Some loose outcome measures, such as the number of children enrolled in a feeding centre, are being used to determine if a feeding centre should continue. In addition, malnutrition prevalence and crude mortality rates determined through nutritional and mortality surveys are used to assess the impact of feeding programs. This procedure does not take into account potential confounding factors that impact on malnutrition prevalence, including access to non-relief foods and the general food ration. Therefore, one could not confidently say that the reduction of malnutrition prevalence is a result of feeding programs. This paper presents an alternative approach to evaluating feeding centres.<br /