IO vs OI in Higher-Order Recursion Schemes

We propose a study of the modes of derivation of higher-order recursion schemes, proving that value trees obtained from schemes using innermost-outermost derivations (IO) are the same as those obtained using unrestricted derivations. Given that higher-order recursion schemes can be used as a model of functional programs, innermost-outermost derivations policy represents a theoretical view point of call by value evaluation strategy.Comment: In Proceedings FICS 2012, arXiv:1202.317

The IO- and OI-hierarchies

AbstractAn analysis of recursive procedures in ALGOL 68 with finite modes shows, that a denotational semantics of this language can be described on the level of program schemes using a typed λ-calculus with fixed-point operators. In the first part of this paper, we derive classical schematological theorems for the resulting class of level-n schemes. In part two, we investigate the language families obtained by call-by-value and call-by-name interpretation of level-n schemes over the algebra of formal languages. It is proved, that differentiating according to the functional level of recursion leads to two infinite hierarchies of recursive languages, the IO- and OI-hierarchies, which can be characterized as canonical extensions of the regular, context-free, and IO- and OI-macro languages, respectively. Sufficient conditions are derived to establish strictness of IO-like hierarchies. Finally we derive, that recursion on higher types induces an infinite hierarchy of control structures by proving that level-n schemes are strictly less powerful than level-n+1 schemes

Contract Aware Components, 10 years after

The notion of contract aware components has been published roughly ten years ago and is now becoming mainstream in several fields where the usage of software components is seen as critical. The goal of this paper is to survey domains such as Embedded Systems or Service Oriented Architecture where the notion of contract aware components has been influential. For each of these domains we briefly describe what has been done with this idea and we discuss the remaining challenges.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Contracts for System Design

Systems design has become a key challenge and differentiating factor over the last decades for system companies. Aircrafts, trains, cars, plants, distributed telecommunication military or health care systems, and more, involve systems design as a critical step. Complexity has caused system design times and costs to go severely over budget so as to threaten the health of entire industrial sectors. Heuristic methods and standard practices do not seem to scale with complexity so that novel design methods and tools based on a strong theoretical foundation are sorely needed. Model-based design as well as other methodologies such as layered and compositional design have been used recently but a unified intellectual framework with a complete design flow supported by formal tools is still lacking albeit some attempts at this framework such as Platform-based Design have been successfully deployed. Recently an "orthogonal" approach has been proposed that can be applied to all methodologies proposed thus far to provide a rigorous scaffolding for verification, analysis and abstraction/refinement: contractbased design. Several results have been obtained in this domain but a unified treatment of the topic that can help in putting contract-based design in perspective is still missing. This paper intends to provide such treatment where contracts are precisely defined and characterized so that they can be used in design methodologies such as the ones mentioned above with no ambiguity. In addition, the paper provides an important link between interfaces and contracts to show similarities and correspondences. Examples of the use of contracts in design are provided as well as in depth analysis of existing literature.Cet article fait le point sur le concept de contrat pour la conception de systèmes. Les contrats que nous proposons portent, non seulement sur des propriétés de typage de leurs interfaces, mais incluent une description abstraite de comportements. Nous proposons une méta-théorie, ou, si l'on veut, une théorie générique des contrats, qui permet le développement séparé de sous-systèmes. Nous montrons que cette méta-théorie se spécialise en l'une ou l'autre des théories connues

Contracts for Systems Design: Theory

Aircrafts, trains, cars, plants, distributed telecommunication military or health care systems,and more, involve systems design as a critical step. Complexity has caused system design times and coststo go severely over budget so as to threaten the health of entire industrial sectors. Heuristic methods andstandard practices do not seem to scale with complexity so that novel design methods and tools based on astrong theoretical foundation are sorely needed. Model-based design as well as other methodologies suchas layered and compositional design have been used recently but a unified intellectual framework with acomplete design flow supported by formal tools is still lacking.Recently an “orthogonal” approach has been proposed that can be applied to all methodologies introducedthus far to provide a rigorous scaffolding for verification, analysis and abstraction/refinement: contractbaseddesign. Several results have been obtained in this domain but a unified treatment of the topic that canhelp in putting contract-based design in perspective is missing. This paper intends to provide such treatmentwhere contracts are precisely defined and characterized so that they can be used in design methodologiessuch as the ones mentioned above with no ambiguity. In addition, the paper provides an important linkbetween interface and contract theories to show similarities and correspondences.This paper is complemented by a companion paper where contract based design is illustrated throughuse cases

Isotope measurements of the Arctic water cycle and exchange processes between seawater, sea ice, and snow during MOSAiC

For the past two decades, the Arctic water cycle changed rapidly due to surface air temperatures (SATs) increasing at twice the global rate. Terrestrial ice (i.e. Greenland Ice Sheet) and marine sea-ice loss, alterations of ocean circulation patterns, and shifting atmospheric moisture sources and transport are some of the most pronounced changes caused by the Arctic amplification, fostering increased humidity levels. Stable water isotopes (δ18O, δ2H) and the secondary parameter d-excess are valuable tracers for hydrological changes, including how these shifts may affect the global climate system. However, it is only recently that we are using precipitation and water vapor networks to resolve water isotope patterns and processes in the Arctic. However, a fully coordinated study of the entire water cycle attributes year-long including sea ice, ocean water, vapor, and precipitation has until recently has been absent. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provided a unique opportunity to collect, analyze, and synthesize discrete samples of the different hydrological compartments in the central Arctic, covering a complete one-year seasonal cycle using a combination of ship-based, the pan-Arctic Water Isotope Network (PAPIN). These observations can lead to new insights into coupled ocean-atmosphere climate processes operating in the Arctic, especially during extreme events, sea ice formation, sea ice retreat, and during a dichotomy of synoptic weather patterns over the MOSAiC-year. We present the isotopic traits of more than 2,200 discrete samples (i.e., seawater, sea ice, snow, brines, frost flowers, lead ice, ridge ice, and precipitation) collected during MOSAiC. Snow has the most depleted δ18O values (-16.3 ± 9.1‰; the number of samples N=306), whereas seawater is the most enriched δ18O compartment (-1.5 ± 0.9‰; N=302) of the Arctic water cycle. Precipitation throughout the Arctic Basin varied from -10‰ to -35‰. Snow profiles are gradually enriched in δ18O from top to bottom by ~20‰ partially due to sublimation of deposited snow, as well as snow metamorphism and its effects on the water isotopes. Second-year ice (SYI) is isotopically relatively depleted in δ18O (-4.2 ± 2.6‰; N=200) compared to first-year ice (FYI) (-0.7 ± 2.1‰; N=635) and insulated FYI (i.e. FYI grown at the bottom of SYI) (-1.7 ± 2.4‰; N=214). The latter is likely caused by post-depositional exchange processes with snow. Open water leads (-1.6 ± 2.4‰; N=137) and melt ponds (-2.1 ± 2.7‰; N=109) on the surface of sea ice contribute to the moistening of the atmosphere in the Arctic on a regional scale. Our dataset provides an unprecedented snapshot of the present-day isotopic composition of the Arctic water cycle during an entire year. The coupling of these discrete samples data with the continuous measurements of atmospheric water vapor may shed light on the relative contribution of snow, sea ice, seawater, open water leads, and melt ponds both spatially and temporally to regional and local moisture levels in the Arctic. Stable water isotopes will ultimately contribute to resolving the linkages between sea ice, ocean, and atmosphere during the critical transition from frozen ocean to open water conditions

Contracts for Systems Design: Methodology and Application cases

Recently, contract based design has been proposed as an ”orthogonal” approach that can beapplied to all methodologies proposed so far to cope with the complexity of system design. Contract baseddesign provides a rigorous scaffolding for verification, analysis and abstraction/refinement. Companionreport RR-8759 proposes a unified treatment of the topic that can help in putting contract-based design in perspective.This paper complements RR-8759 by further discussing methodological aspects of system design withcontracts in perspective and presenting two application cases.The first application case illustrates the use of contracts in requirement engineering, an area of system designwhere formal methods were scarcely considered, yet are stringently needed. We focus in particular to thecritical design step by which sub-contracts are generated for suppliers from a set of different viewpoints(specified as contracts) on the global system. We also discuss important issues regarding certification inrequirement engineering, such as consistency, compatibility, and completeness of requirements.The second example is developed in the context of the Autosar methodology now widely advocated inthe automotive sector. We propose a contract framework to support schedulability analysis, a key step inAutosar methodology. Our aim differs from the many proposals for compositional schedulability analysisin that we aim at defining sub-contracts for suppliers, not just performing the analysis by parts—we knowfrom companion paper RR-8759 that sub-contracting to suppliers differs from a compositional analysis entirelyperformed by the OEM. We observe that the methodology advocated by Autosar is in contradiction withcontract based design in that some recommended design steps cannot be refinements. We show how tocircumvent this difficulty by precisely bounding the risk at system integration phase. Another feature ofthis application case is the combination of manual reasoning for local properties and use of the formalcontract algebra to lift a collection of local checks to a system wide analysis

Gestational diabetes: determination of risk factors to diabetes mellitus

Objetivos Identificar fatores preditivos do desenvolvimento de diabetes mellitus (DM) em mulheres com antecedentes de diabetes gestacional (DG). Tipo de estudo Estudo observacional, analítico, retrospetivo e de coorte. Local Hospital de Braga. População Amostra aleatória de 300 mulheres, nascidas antes de 1995, com diagnóstico de DG entre 1 de janeiro de 2001 e 31 de dezembro de 2010 e seguimento da gravidez no Hospital de Braga. Métodos Os dados foram obtidos através da consulta de processos clínicos. A lista de doentes com DM, referente ao ano de 2011, foi utilizada para verificação do desenvolvimento da doença no grupo selecionado. Foram analisados o perfil sociodemográfico, os antecedentes pessoais, familiares e obstétricos e outros fatores anteparto. Foi realizada uma análise descritiva univariada e bivariada. Seguidamente foi criado um modelo de regressão logística binária para identificar potenciais preditores de desenvolvimento de DM tipo 2. Resultados Trinta e dois vírgula sete por cento das mulheres desenvolveu DM. A probabilidade de desenvolvimento de DM após DG aumentou 8,2 vezes quando idade gestacional menor que 24 semanas no momento do diagnóstico (OR = 8,19; p < 0,001), 3,4 vezes se necessidade de insulinoterapia (OR = 3,36; p < 0,001) e 3,1 vezes se índice de massa corporal (IMC) prévio = 26,4 kg/m2 (OR = 3,07; p = 0,003). História familiar de DM tipo 2, 4 valores elevados na prova de tolerância oral à glicose, valor de glicemia em jejum, idade materna no momento do diagnóstico e IMC pós-parto, apesar de apresentarem associação com desenvolvimento de DM não se revelaram seus preditores. Não se verificou associação entre gravidez prévia ou diagnóstico prévio de DG com desenvolvimento de DM. Conclusões Em mulheres com DG, a idade gestacional menor que 24 semanas no momento do diagnóstico, a necessidade de insulinoterapia e o IMC prévio = 26,4 kg/m2 apresentaram-se como fatores de risco para desenvolvimento de DM.Aims: To identify predictive factors to diabetes mellitus (DM) development in women with history of gestational diabetes (GD). Study design: An observational, analytic, cohort retrospective study. Local: Hospital of Braga. Population: A random sample of 300 women, born before 1995, with GD diagnosed since January 1, 2001 to December 31, 2010 and pregnancy surveillance in a public Hospital of Braga. Methods: Data was collected by consultation of medical records. The DM patients’ list of 2011 was used to verification of the disease development in the selected group. Sociodemographic profile, personal, family and obstetric history, and other antepartum factors were analyzed. A univariate descriptive analysis and a bivariate analysis were performed. A binary logistic regression model was created to identify potential predictors of type 2 DM development. Results: 32.7% of women developed DM. The probability of DM development after GD was increased 8.2 times when gestational age at diagnosis was less than 24 weeks (OR = 8.19; p < 0.001), 3.4 times with the need of insulin therapy (OR = 3.36; p < 0.001) and 3.1 times with previous pregnancy body mass index (BMI) ≥ 26.4 kg/m2 (OR = 3.07; p = 0.003). Although family history of type 2 DM, maternal age at diagnosis, postpartum BMI, 4 abnormal values in the diagnostic oral glucose tolerance test and fasting glucose level had presented association with DM development, did not present as its predictors. It was not verified association between previous pregnancy or previous GD diagnosis and DM development. Conclusions: In women with GD, gestational age at diagnosis less than 24 weeks, need of insulin therapy and previous pregnancy BMI ≥ 26.4 kg/m2 were presented as risk factors to DM development. © 2014 Sociedade Portuguesa de Endocrinologia, Diabetes e Metabolismo. Published by Elsevier España