Denotational semantics in Synthetic Guarded Domain Theory

In functional programming, features such as recursion, recursive types and general references are central. To define semantics of this kind of languages one needs to come up with certain definitions which may be non-trivial to show well-defined. This is because they are circular. Domain theory has been used to solve this kind of problems for specific languages, unfortunately, this technique does not scale for more featureful languages, which prevented it from being widely used. Step-indexing is a more general technique that has been used to break circularity of definitions. The idea is to tweak the definition by adding a well-founded structure that gives a handle for recursion. Guarded dependent Type Theory (gDTT) is a type theory which implements step-indexing via a unary modality used to guard recursive definitions. Every circular definition is well-defined as long as the recursive variable is guarded. In this thesis we show that gDTT is a natural setting to give denotational semantics of typed functional programming languages with recursion and recursive types. We formulate operational semantics and denotational semantics and prove computational adequacy entirely inside the type theory. Furthermore, our interpretation is synthetic: types are interpreted as types in the type theory and programs as type-theoretical terms. Moreover, working directly in gDTT has advantages compared with existing set-theoretic models. Finally, this work builds the foundations for doing denotational semantics of languages with much more challenging features, for example, of general references for which denotational techniques were previously beyond reach

IMAGINE Project: Urban Measurements of Lden and Lnight and Calculation of the Associated Uncertainties

This article describes the principles of the new measurement method developed within the IMAGINE European project to determine Lden and Lnight, as defined by the European Noise Directive 2002/49/EC, by direct measurement of the noise levels. The measurement method was tested in a real and complex urban environment including a major road, a major railway line and an industrial site. A description is given for the calculation of the yearly averaged levels and the uncertainty estimation. Concerning such long term indicators, estimation of uncertainty is a rather complex task, especially if the yearly Lden and Lnight are derived from measurements performed over a short period of the year. The uncertainties concern the microphone position, the source variation, the meteorological variations, the correction for background noise and the sound level meter class 1 uncertainty. The example described here is based on a measurement campaign performed over one year in the city of Pisa (Italy).The aforementioned measurements would be typically applied to support the credibility of noise map calculations towards the citizens and to validate calculations of noise maps in well-defined situations.JRC.I.5-Physical and chemical exposure

Formally verifying Exceptions for Low-level code with Separation Logic

Exceptions in low-level architectures are implemented as synchronous interrupts: upon the execution of a faulty instruction the processor jumps to a piece of code that handles the error. Previous work has shown that assembly programs can be written, verified and run using higher-order separation logic. However, execution of faulty instructions is then specified as either being undefined or terminating with an error. In this paper, we study synchronous interrupts and show their usefulness by implementing a memory allocator. This shows that it is indeed possible to write positive specifications of programs that fault. All of our results are mechanised in the interactive proof assistant Coq

VTN: A VALIDATED METHOD TO SEPARATE TRACK AND VEHICLE NOISE AND TO ASSESS NOISE REDUCTION MEASURES

Abstract Within the European project STAIRRS, new methods and tools have been developed to address particular needs in the measurement and characterisation of railway noise. The Vibro-acoustic Track Noise method (VTN) is one of these methods. It is capable of separating the noise radiated by the train from the noise radiated by the track. The method uses a small number of acceleration signals from the rails and sleepers to calculate the energy radiation from the track. By measuring the total noise emitted by vehicle and track, it is possible to calculate the vehicle contribution as well. The method has been validated in the STAIRRS project and its accuracy has been assessed. Comparisons with results from TWINS calculations give further information about the accuracy of the method. The VTN-method has been programmed as a PC-based analysis tool. The tool has demonstrated its capabilities in the assessment of noise reduction measures. It clearly visualises the extent to which a measure acts on either the vehicle emission or the track emission. This makes it possible to assess the effect of that measure for combinations of other trains and tracks that were not tested. If the effect on the total noise is rather small (< 2 dB(A)), studying the VTN results can point out whether the effect is real. Other applications of VTN are acceptance and limit conformance testing and the collection of emission data (monitoring). The separated results make it possible to attribute the responsibility of railway noise emission to the track maintainer on the one hand and the train operator on the other hand

Proceedings of the International Workshop on 'Combined Environmental Exposure: Noise, Air Pollutants and Chemicals'

The issue of combined exposure to noise, air pollution and chemicals has raised recently the interest of several bodies of the European Commission such as DG Environment, DG SANCO and DG Research in the context of the EC 7th Framework Programme. There are open questions whether prevailing environmental concentrations of air pollutants and chemicals can lead to ototoxic health impacts. Therefore this issue needs to be thoroughly explored and investigated to help the EC to revise the existing standards and guidelines concerning combined exposure to noise, air pollutants and chemicals. The aim of the workshop was to review and discuss the existing scientific evidence whether prevailing environmental exposures to single and concomitant agents together with noise could lead to ototoxic or other health impacts. The final aim was to identify the research needs and to give recommendations for research and policy making in the EU level. It was agreed that research in the future should be focused on really established combinations (high correlations) and interactions (known effect) with main perspective on the traffic bundle of exposure. It was also discussed and agreed upon that the best knowledge exists on the health effects due to combined exposure to noise and solvents or heavy metals in occupational environments, especially on most of the auditory and non-auditory effects. Possible factors that may have confounding or aggravating effects on the results of noise studies were identified. Such factors are: age, gender, smoking, obesity, alcohol, socio-economic status, occupation, education, family status, active military, experience, hereditary disease, medication, medical status, race and ethnicity, physical activity, noisy leisure activities, stress reducing activities, diet & nutrition, housing condition (crowding), and residential status. Research priorities and recommendations for the future. The highest priority was given to issues related to research on noise and outdoor air pollutants. This is due to the fact that it may concern the largest population compared to the other stressors in this analysis and there is some evidence of serious health outcomes such as cardiovascular effects. The next priority was given to the research on the effects of noise and solvents in occupational settings and to research on noise and organophosphates. In the future research, priority should be given to: 1. evaluation of existing data collections whether re-analyses are possible with respect to combined exposure from traffic sources (road, rail and air), 2. analyses of existing data concerning noise and other stressors interactions in both occupational and environmental settings, 3. detailed assessment of combined exposures to noise, vibrations and PM, CO, NOx, and VOCs with specific studies in urban areas and, especially, cardiovascular health endpoints should be studied as priority health endpoints, 4. identification of causal mechanisms through careful review of toxicological experimental studies.JRC.I.5-Physical and chemical exposure

Denotational semantics of recursive types in synthetic guarded domain theory

Just like any other branch of mathematics, denotational semantics of programming languages should be formalised in type theory, but adapting traditional domain theoretic semantics, as originally formulated in classical set theory to type theory has proven challenging. This paper is part of a project on formulating denotational semantics in type theories with guarded recursion. This should have the benefit of not only giving simpler semantics and proofs of properties such as adequacy, but also hopefully in the future to scale to languages with advanced features, such as general references, outside the reach of traditional domain theoretic techniques. Working in Guarded Dependent Type Theory (GDTT), we develop denotational semantics for FPC, the simply typed lambda calculus extended with recursive types, modelling the recursive types of FPC using the guarded recursive types of GDTT. We prove soundness and computational adequacy of the model in GDTT using a logical relation between syntax and semantics constructed also using guarded recursive types. The denotational semantics is intensional in the sense that it counts the number of unfold-fold reductions needed to compute the value of a term, but we construct a relation relating the denotations of extensionally equal terms, i.e., pairs of terms that compute the same value in a different number of steps. Finally we show how the denotational semantics of terms can be executed inside type theory and prove that executing the denotation of a boolean term computes the same value as the operational semantics of FPC

Denotational semantics in Synthetic Guarded Domain Theory

In functional programming, features such as recursion, recursive types and general references are central. To define semantics of this kind of languages one needs to come up with certain definitions which may be non-trivial to show well-defined. This is because they are circular. Domain theory has been used to solve this kind of problems for specific languages, unfortunately, this technique does not scale for more featureful languages, which prevented it from being widely used. Step-indexing is a more general technique that has been used to break circularity of definitions. The idea is to tweak the definition by adding a well-founded structure that gives a handle for recursion. Guarded dependent Type Theory (gDTT) is a type theory which implements step-indexing via a unary modality used to guard recursive definitions. Every circular definition is well-defined as long as the recursive variable is guarded. In this thesis we show that gDTT is a natural setting to give denotational semantics of typed functional programming languages with recursion and recursive types. We formulate operational semantics and denotational semantics and prove computational adequacy entirely inside the type theory. Furthermore, our interpretation is synthetic: types are interpreted as types in the type theory and programs as type-theoretical terms. Moreover, working directly in gDTT has advantages compared with existing set-theoretic models. Finally, this work builds the foundations for doing denotational semantics of languages with much more challenging features, for example, of general references for which denotational techniques were previously beyond reach

Denotational semantics of recursive types in synthetic guarded domain theory

Guarded recursion is a form of recursion where recursive calls are guarded by delay modalities. Previous work has shown how guarded recursion is useful for reasoning operationally about programming languages with advanced features including general references, recursive types, countable non-determinism and concurrency. Guarded recursion also offers a way of adding recursion to type theory while maintaining logical consistency. In previous work we initiated a programme of denotational semantics in type theory using guarded recursion, by constructing a computationally adequate model of the language PCF (simply typed lambda calculus with fixed points). This model was intensional in that it could distinguish between computations computing the same result using a different number of fixed point unfoldings. In this work we show how also programming languages with recursive types can be given denotational semantics in type theory with guarded recursion. More precisely, we give a computationally adequate denotational semantics to the language FPC (simply typed lambda calculus extended with recursive types), modelling recursive types using guarded recursive types. The model is intensional in the same way as was the case in previous work, but we show how to recover extensionality using a logical relation. All constructions and reasoning in this paper, including proofs of theorems such as soundness and adequacy, are by (informal) reasoning in type theory, often using guarded recursion

Expected Mean in an Environmental Noise Measurement and its Related Uncertainty

In the context of the implementation of the Environmental Noise Directive 2002/49/EC a study on noise measurement uncertainty was performed. Averaging over different samples of noise measurements , there might be assumptions over the distribution and independency of the samples. In the context of environmental noise, this might be the case of a series of measurements of a constant noise source like an industrial plant or a fluctuating noise source like road traffic. Using a series of 15 minutes LAeq samples, the average of these values is usually considered as the expected mean, however, the error caused by the specific selection of the samples is not usually evaluated. Statistically speaking, before establishing an average value, at least the distribution of the samples and the effect of adding-up several uncertainties should be evaluated. This article focuses on the mathematical formulas which could be used and discusses the differences in assessing the expected mean for normally distributed values, or for log-normally distributed, and finally suggests an approach to properly adding-up all uncertainties related to a long-term environmental noise measurement campaign.JRC.I.2-Chemical assessment and testin

Advancement in the development of European common noise assessment methods: where are we?

In the context of the European Environmental Noise Directive (2002/49/EC)1, to improve the quality and reliability of the overall noise assessment results, the European Commission intends to prepare common noise assessment method for road traffic, railway traffic, aircraft and industrial noise, including guidelines on method implementation and input data, aimed at obtaining comparable results across the EU Member States. A roadmap for preparing the common noise assessment methods was established by DG ENV of the European Commission. This includes the identification and evaluation of existing methods on the basis of the following criteria: (a) ability to consider differences in noise source amongst EU regions (specific features which vary due to environmental factors like road and railway surface maintenance, specific regulations in force, techniques used to prevent noise, road & railway networks and aircrafts fleets); (b) ability to consider meteorological effects; easiness of implementation; (c) availability free of intellectual property rights; (d) integration of scientific evidence; (e) availability and quality of input data; (f) fulfilment of the requirements of the END. In the period December 2008 to August 2009, DG JRC in co-operation with the European Environment Agency elaborated requirements on the input values and their associated quality in view of the next round of European noise mapping and identified and scrutinised the noise assessment methods that best cover the needs and requirements of the END with regard to strategic noise mapping. These preselected methods were proposed to DG ENV for further consideration for establishing the common noise assessment methods in EU. In a second step, those parts of the selected methods that fulfil at best the criteria of the evaluation will be used to produce a ¿fit for purpose¿ framework for common European noise assessment method(s).JRC.DG.I.2-Chemical assessment and testin