Regular Expression Matching and Operational Semantics

Many programming languages and tools, ranging from grep to the Java String library, contain regular expression matchers. Rather than first translating a regular expression into a deterministic finite automaton, such implementations typically match the regular expression on the fly. Thus they can be seen as virtual machines interpreting the regular expression much as if it were a program with some non-deterministic constructs such as the Kleene star. We formalize this implementation technique for regular expression matching using operational semantics. Specifically, we derive a series of abstract machines, moving from the abstract definition of matching to increasingly realistic machines. First a continuation is added to the operational semantics to describe what remains to be matched after the current expression. Next, we represent the expression as a data structure using pointers, which enables redundant searches to be eliminated via testing for pointer equality. From there, we arrive both at Thompson's lockstep construction and a machine that performs some operations in parallel, suitable for implementation on a large number of cores, such as a GPU. We formalize the parallel machine using process algebra and report some preliminary experiments with an implementation on a graphics processor using CUDA.Comment: In Proceedings SOS 2011, arXiv:1108.279

Projected health effects of realistic dietary changes to address freshwater constraints in India : a modelling study

Acknowledgements This study forms part of the Sustainable and Healthy Diets in India project supported by the Wellcome Trust's Our Planet, Our Health programme (grant number 103932). LA's PhD is funded by the Leverhulme Centre for Integrative Research on Agriculture and Health. SA is supported by a Wellcome Trust Capacity Strengthening Strategic Award-Extension phase (grant number WT084754/Z/08/A). We would like to thank Zaid Chalabi (London School of Hygiene & Tropical Medicine) for providing valuable guidance on the modelling methods.Peer reviewedPublisher PD

Dietary patterns in India: a systematic review.

Dietary patterns analysis is an emerging area of research. Identifying distinct patterns within a large dietary survey can give a more accurate representation of what people are eating. Furthermore, it allows researchers to analyse relationships between non-communicable diseases (NCD) and complete diets rather than individual food items or nutrients. However, few such studies have been conducted in developing countries including India, where the population has a high burden of diabetes and CVD. We undertook a systematic review of published and grey literature exploring dietary patterns and relationships with diet-related NCD in India. We identified eight studies, including eleven separate models of dietary patterns. Most dietary patterns were vegetarian with a predominance of fruit, vegetables and pulses, as well as cereals; dietary patterns based on high-fat, high-sugar foods and more meat were also identified. There was large variability between regions in dietary patterns, and there was some evidence of change in diets over time, although no evidence of different diets by sex or age was found. Consumers of high-fat dietary patterns were more likely to have greater BMI, and a dietary pattern high in sweets and snacks was associated with greater risk of diabetes compared with a traditional diet high in rice and pulses, but other relationships with NCD risk factors were less clear. This review shows that dietary pattern analyses can be highly valuable in assessing variability in national diets and diet-disease relationships. However, to date, most studies in India are limited by data and methodological shortcomings

Cultural connections: The Role of the Arts and Humanities in Competitiveness and Local Development

This report considers how the arts and cultural institutions contribute to the appeal of place. Cultural institutions are a prominent part of UK society – and many have a rich and long heritage. The impact of such institutions has often been evaluated in terms of engagement and participation or on the direct economic impact of cultural institutions. This study primarily focuses on the wider role of cultural institutions in their local economies; their innovative activities; how they connect to other local organisations such as universities; and how they collaborate with academics from the Arts and Humanities

Model Order Reduction for UCERF3-TD for Loss Exceedance

The Uniform California Earthquake Rupture Forecast version 3-Time Dependent is a complexmathematical model of where California&rsquo;s seismic faults are and how frequently they produceearthquakes. The model is represented by a logic tree with 5,760 leaves, each representing onecombination of modeling choices to represent epistemic uncertainties. To use the model in riskanalysis, one must often add epistemic uncertainties, such as which of several ground-motionpredictionequations to use. Doing so can increase the model size to 172,800 leaves. Each leaf stillhas explicit uncertainties, often called aleatory uncertainties, such as whether each of 6 millionpossible earthquakes will occur and the resulting map of spatially correlated shaking. To use themodel in practice with all these uncertainties can be computationally demanding. It is desirable tofind a subset of epistemic uncertainties that preserve the distribution of important dependentvariables. We previously showed how to trim the logic tree to preserve the distribution of expectedannualized repair cost to a large portfolio of California buildings. Here we show how to trim thelogic tree to preserve the distributions of expected annualized repair cost and of loss with variousrare exceedance frequencies: 1 time in 100 years, 250 years, 400 years, 550 years, and 2,500 years.It appears that one can reduce the logic tree to as few as 15 logic tree leaves (from 172,800),varying only ground motion model and ground motion model added epistemic uncertainty, at leastfor the 400-year and 550-year losses. A hypothetical risk calculation that takes 24 hours for thefull model (evaluating all 172,800 leaves) can be reduced to a calculation that takes 8 seconds (fora reduced-order model with 15 leaves). But in all cases examined here, one can trim the logic treeby at least three variables. Because of the exponential relationship between the number of logictree branches and the size of the model, even trimming three variables can produce a huge savingsin computational effort, reducing the number of logic tree leaves to 4% of the size of the full model.Model order reduction can have important financial benefits. With more study, it may be possibleto reduce uncertainty around the choice of ground motion model and of added epistemicuncertainty in the ground motion model. Lower uncertainty means thinner tails to the distributionof loss, that is, lower loss associated with rare exceedance rates. If an insurer can reduce itsestimate of rare loss, it can buy less reinsurance and save money.</p

Health effects of adopting low greenhouse gas emission diets in the UK.

OBJECTIVE: Dietary changes which improve health are also likely to be beneficial for the environment by reducing emissions of greenhouse gases (GHG). However, previous analyses have not accounted for the potential acceptability of low GHG diets to the general public. This study attempted to quantify the health effects associated with adopting low GHG emission diets in the UK. DESIGN: Epidemiological modelling study. SETTING: UK. PARTICIPANTS: UK population. INTERVENTION: Adoption of diets optimised to achieve the WHO nutritional recommendations and reduce GHG emissions while remaining as close as possible to existing dietary patterns. MAIN OUTCOME: Changes in years of life lost due to coronary heart disease, stroke, several cancers and type II diabetes, quantified using life tables. RESULTS: If the average UK dietary intake were optimised to comply with the WHO recommendations, we estimate an incidental reduction of 17% in GHG emissions. Such a dietary pattern would be broadly similar to the current UK average. Our model suggests that it would save almost 7 million years of life lost prematurely in the UK over the next 30 years and increase average life expectancy by over 8 months. Diets that result in additional GHG emission reductions could achieve further net health benefits. For emission reductions greater than 40%, improvements in some health outcomes may decrease and acceptability will diminish. CONCLUSIONS: There are large potential benefits to health from adopting diets with lower associated GHG emissions in the UK. Most of these benefits can be achieved without drastic changes to existing dietary patterns. However, to reduce emissions by more than 40%, major dietary changes that limit both acceptability and the benefits to health are required

Several types of types in programming languages

Types are an important part of any modern programming language, but we often forget that the concept of type we understand nowadays is not the same it was perceived in the sixties. Moreover, we conflate the concept of "type" in programming languages with the concept of the same name in mathematical logic, an identification that is only the result of the convergence of two different paths, which started apart with different aims. The paper will present several remarks (some historical, some of more conceptual character) on the subject, as a basis for a further investigation. The thesis we will argue is that there are three different characters at play in programming languages, all of them now called types: the technical concept used in language design to guide implementation; the general abstraction mechanism used as a modelling tool; the classifying tool inherited from mathematical logic. We will suggest three possible dates ad quem for their presence in the programming language literature, suggesting that the emergence of the concept of type in computer science is relatively independent from the logical tradition, until the Curry-Howard isomorphism will make an explicit bridge between them.Comment: History and Philosophy of Computing, HAPOC 2015. To appear in LNC

Mutual shaping in swarm robotics: User studies in fire and rescue, storage organization, and bridge inspection

Many real-world applications have been suggested in the swarm robotics literature. However, there is a general lack of understanding of what needs to be done for robot swarms to be useful and trusted by users in reality. This paper aims to investigate user perception of robot swarms in the workplace, and inform design principles for the deployment of future swarms in real-world applications. Three qualitative studies with a total of 37 participants were done across three sectors: fire and rescue, storage organization, and bridge inspection. Each study examined the users’ perceptions using focus groups and interviews. In this paper, we describe our findings regarding: the current processes and tools used in these professions and their main challenges; attitudes toward robot swarms assisting them; and the requirements that would encourage them to use robot swarms. We found that there was a generally positive reaction to robot swarms for information gathering and automation of simple processes. Furthermore, a human in the loop is preferred when it comes to decision making. Recommendations to increase trust and acceptance are related to transparency, accountability, safety, reliability, ease of maintenance, and ease of use. Finally, we found that mutual shaping, a methodology to create a bidirectional relationship between users and technology developers to incorporate societal choices in all stages of research and development, is a valid approach to increase knowledge and acceptance of swarm robotics. This paper contributes to the creation of such a culture of mutual shaping between researchers and users, toward increasing the chances of a successful deployment of robot swarms in the physical realm