582 research outputs found
CamFlow: Managed Data-sharing for Cloud Services
A model of cloud services is emerging whereby a few trusted providers manage
the underlying hardware and communications whereas many companies build on this
infrastructure to offer higher level, cloud-hosted PaaS services and/or SaaS
applications. From the start, strong isolation between cloud tenants was seen
to be of paramount importance, provided first by virtual machines (VM) and
later by containers, which share the operating system (OS) kernel. Increasingly
it is the case that applications also require facilities to effect isolation
and protection of data managed by those applications. They also require
flexible data sharing with other applications, often across the traditional
cloud-isolation boundaries; for example, when government provides many related
services for its citizens on a common platform. Similar considerations apply to
the end-users of applications. But in particular, the incorporation of cloud
services within `Internet of Things' architectures is driving the requirements
for both protection and cross-application data sharing.
These concerns relate to the management of data. Traditional access control
is application and principal/role specific, applied at policy enforcement
points, after which there is no subsequent control over where data flows; a
crucial issue once data has left its owner's control by cloud-hosted
applications and within cloud-services. Information Flow Control (IFC), in
addition, offers system-wide, end-to-end, flow control based on the properties
of the data. We discuss the potential of cloud-deployed IFC for enforcing
owners' dataflow policy with regard to protection and sharing, as well as
safeguarding against malicious or buggy software. In addition, the audit log
associated with IFC provides transparency, giving configurable system-wide
visibility over data flows. [...]Comment: 14 pages, 8 figure
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A Market-Based Approach to Software Evolution
Software correctness has bedeviled the field of computer science since its inception. Software complexity has increased far more quickly than our ability to control it, reaching sizes that are many orders of magnitude beyond the reach of formal or automated verification techniques.
We propose a new paradigm for evaluating "correctness" based on a rich market ecosystem in which coalitions of users bid for features and fixes. Developers, testers, bug reporters, and analysts share in the rewards for responding to those bids. In fact, we suggest that the entire software development process can be driven by a disintermediated market-based mechanism driven by the desires of users and the capabilities of developers.
The abstract, unspecifiable, and unknowable notion of absolute correctness is then replaced by quantifiable notions of correctness demand (the sum of bids for bugs) and correctness potential (the sum of the available profit for fixing those bugs). We then sketch the components of a market design intended to identify bugs, elicit demand for fixing bugs, and source workers for fixing bugs. The ultimate goal is to achieve a more appropriate notion of correctness, in which market forces drive software towards a correctness equilibrium in which all bugs for which there is enough value, and with low enough cost to fix, are fixed.Engineering and Applied Science
EC80-553 What to Do Until the Doctor Comes....First Aid : A Guide for Emergency Medical Care
Extension circular 80-553 discusses What to do until the doctor comes: first aid, a guide for emergency medical care
On the validity of the Born approximation for weak cosmic flexions
Weak lensing calculations are often made under the assumption of the Born approximation, where the ray path is approximated as a straight radial line. In addition, lens-lens couplings where there are several deflections along the light ray are often neglected. We examine the effect of dropping the Born approximation and taking lens-lens couplings into account, for weak lensing effects up to second order (cosmic flexion), by making a perturbative expansion in the light path. We present a diagrammatic representation of the resulting corrections to the lensing effects. The flexion signal, which measures the derivative of the density field, acquires correction terms proportional to the squared gravitational shear; we also find that by dropping the Born approximation, two further degrees of freedom of the lensing distortion can be excited (the twist components), in addition to the four standard flexion components. We derive angular power spectra of the flexion and twist, with and without the Born approximation and lens-lens couplings and confirm that the Born approximation is an excellent approximation for weak cosmic flexions, but may fail in the strong lensing regim
Growing a Software Language for Hardware Design
The Liquid Metal project at IBM Research aimed to design and implement a new programming language called Lime to address some of the challenges posed by heterogeneous systems. Lime is a Java-compatible programming language with features designed to facilitate high level synthesis to hardware (FPGAs). This article reviews the language design from the outset, and highlights some of the earliest design decisions. We also describe how these decisions were revised recently to accommodate important requirements that arise in networking and cryptography
On the validity of the Born approximation for weak cosmic flexions
Weak lensing calculations are often made under the assumption of the Born
approximation, where the ray path is approximated as a straight radial line. In
addition, lens-lens couplings where there are several deflections along the
light ray are often neglected. We examine the effect of dropping the Born
approximation and taking lens-lens couplings into account, for weak lensing
effects up to second order (cosmic flexion), by making a perturbative expansion
in the light path. We present a diagrammatic representation of the resulting
corrections to the lensing effects. The flexion signal, which measures the
derivative of the density field, acquires correction terms proportional to the
squared gravitational shear; we also find that by dropping the Born
approximation, two further degrees of freedom of the lensing distortion can be
excited (the twist components), in addition to the four standard flexion
components. We derive angular power spectra of the flexion and twist, with and
without the Born-approximation and lens-lens couplings and confirm that the
Born approximation is an excellent approximation for weak cosmic flexions,
except at very small scales.Comment: 12 pages, 5 figures, submitted to MNRA
Adapting Cohort-Component Methods to a Microsimulation: A case study
Social scientists generally take United Nations (UN) population projections as the baseline when considering the potential impact of any changes that could affect fertility, mortality or migration, and the UN typically does projections using the cohort-component method (CCM). The CCM technique is computationally simple and familiar to demographers. However, in order to avoid the exponential expansion of complexity as new dimensions of individual difference are added to projections, and to understand the sensitivity of projections to specific conditions, agent-based microsimulations are a better option. CCMs can mask hidden assumptions that are surfaced by the construction of microsimulations, and varying such assumptions can lead to quite different projections. CCM models are naturally the strongest form of validation for population projection microsimulations but there are many complexities and difficulties associated with matching microsimulation projections and CCM projections. Here, we describe our efforts to tackle these challenges as we validated a microsimulation for Norway by replicating a UN CCM projection. This provides guidance for other simulationists who seek to use CCMs to validate microsimulations. More importantly, it demonstrates the value of microsimulations for surfacing assumptions that frequently lie hidden, and thus unevaluated, within CCM projections.publishedVersio
Adapting Cohort-Component Methods to a Microsimulation: A case study
Social scientists generally take United Nations (UN) population projections as the baseline when considering the potential impact of any changes that could affect fertility, mortality or migration, and the UN typically does projections using the cohort-component method (CCM). The CCM technique is computationally simple and familiar to demographers. However, in order to avoid the exponential expansion of complexity as new dimensions of individual difference are added to projections, and to understand the sensitivity of projections to specific conditions, agent-based microsimulations are a better option. CCMs can mask hidden assumptions that are surfaced by the construction of microsimulations, and varying such assumptions can lead to quite different projections. CCM models are naturally the strongest form of validation for population projection microsimulations but there are many complexities and difficulties associated with matching microsimulation projections and CCM projections. Here, we describe our efforts to tackle these challenges as we validated a microsimulation for Norway by replicating a UN CCM projection. This provides guidance for other simulationists who seek to use CCMs to validate microsimulations. More importantly, it demonstrates the value of microsimulations for surfacing assumptions that frequently lie hidden, and thus unevaluated, within CCM projections.publishedVersio
Energy dependence of {\rm K} and hyperon production at CERN SPS
Recent results on K and hyperon production in Pb-Pb collisions at
40 and 158 GeV/ beam momentum from the NA57 experiment at CERN SPS are
presented. Yields and ratios are compared with those measured by the NA49
experiment, where available. The centrality dependence of the yields and a
comparison with the higher collision energy data from RHIC are discussed.Comment: 4 pages, 3 figures, proceedings of QM2004 conferenc
Interactions of Bacillus Mojavensis and Fusarium Verticillioides With a Benzoxazolinone (Boa) and Its Transformation Product, Apo
En:Journal of Chemical Ecology (2007, vol. 33, n. 10, p. 1885-1897)The benzoxazolinones, specifically benzoxazolin-2(3H)-one (BOA), are important transformation products of the benzoxazinones that can serve as allelochemicals providing resistance to maize from pathogenic bacteria, fungi, and insects. However, maize pathogens such as Fusarium verticillioides are capable of detoxifying the benzoxazolinones to 2-aminophenol (AP), which is converted to the less toxic N-(2-hydroxyphenyl) malonamic acid (HPMA) and 2-acetamidophenol (HPAA). As biocontrol strategies that utilize a species of endophytic bacterium, Bacillus mojavensis, are considered efficacious as a control of this Fusarium species, the in vitro transformation and effects of BOA on growth of this bacterium was examined relative to its interaction with strains of F. verticillioides. The results showed that a red pigment was produced and accumulated only on BOA-amended media when wild type and the progeny of genetic crosses of F. verticillioides are cultured in the presence of the bacterium. The pigment was identified as 2-amino-3H-phenoxazin-3-one (APO), which is a stable product. The results indicate that the bacterium interacts with the fungus preventing the usual transformation of AP to the nontoxic HPMA, resulting in the accumulation of higher amounts of APO than when the fungus is cultured alone. APO is highly toxic to F. verticillioides and other organisms. Thus, an enhanced biocontrol is suggested by this in vitro study.
=580 $aEn:Journal of Chemical Ecolog
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