Determining the quality of mathematical software using reference data sets

This paper describes a methodology for evaluating the numerical accuracy of software that performs mathematical calculations. The authors explain how this methodology extends the concept of metrological traceability, which is fundamental to measurement, to include software quality. Overviews of two European Union-funded projects are also presented. The first project developed an infrastructure to allow software to be verified by testing, via the internet, using reference data sets. The primary focus of the project was software used within systems that make physical measurements. The second project, currently underway, explores using this infrastructure to verify mathematical software used within general scientific and engineering disciplines. Publications on using reference data sets for the verification of mathematical software are usually intended for a readership specialising in measurement science or mathematics. This paper is aimed at a more general readership, in particular software quality specialists and computer scientists. Further engagement with experts in these disciplines will be helpful to the continued development of this application of software quality

Deep space experiment to measure GG

Responding to calls from the National Science Foundation (NSF) for new proposals to measure the gravitational constant $G$, we offer an interesting experiment in deep space employing the classic gravity train mechanism. Our setup requires three bodies: a larger layered solid sphere with a cylindrical hole through its center, a much smaller retroreflector which will undergo harmonic motion within the hole and a host spacecraft with laser ranging capabilities to measure round trip light-times to the retroreflector but ultimately separated a significant distance away from the sphere-retroreflector apparatus. Measurements of the period of oscillation of the retroreflector in terms of host spacecraft clock time using existing technology could give determinations of $G$ nearly three orders of magnitude more accurate than current measurements here on Earth. However, significant engineering advances in the release mechanism of the apparatus from the host spacecraft will likely be necessary. Issues with regard to the stability of the system are briefly addressed.Comment: 13 pp, 3 figs, accepted CQ

School-to-Career Programs and Transitions to Employment and Higher Education

The 1994 Federal School-to-Work Opportunities Act (STWOA) provided more than $1.5 billion over five years to support increased career preparation activities in the country's public schools. However, the STWOA was not re-authorized, so state governments face decisions about levels of funding support for school-to-career (STC) programs. Coupled with the availability of a new longitudinal data source with rich information on STC programs the 1997 National Longitudinal Survey of Youth (NLSY97) it is therefore an opportune time to study the effectiveness of STC programs. This paper uses the NLSY97 to assess the effects of STC programs on transitions to employment and higher education among youths leaving high school, with a focus on estimating the causal effects of this participation given possible non-random selection of youths into STC programs.

Disabled or Young? Relative Age and Special Education Diagnoses in Schools

This study extends recent findings of a relationship between the relative age of students among their peers and their probability of disability classification. Using three nationally representative surveys spanning 1988-2004 and grades K-10, we find that an additional month of relative age decreases the likelihood of receiving special education services by 2-5 percent. Relative age effects are strong for learning disabilities but not for other disabilities. We measure them for boys starting in kindergarten but not for girls until 3rd grade. We also measure them for white and Hispanic students but not for black students or differentially by socioeconomic quartiles. Results are consistent with the interpretation that disability assessments do not screen for the possibility that relatively young students are over-referred for evaluation. Lastly, we present suggestive evidence that math achievement gains due to disability classification may differentially benefit relatively young students.Education, Relative Age, Special Education

Facile: a command-line network compiler for systems biology

<p>Abstract</p> <p>Background</p> <p>A goal of systems biology is the quantitative modelling of biochemical networks. Yet for many biochemical systems, parameter values and even the existence of interactions between some chemical species are unknown. It is therefore important to be able to easily investigate the effects of adding or removing reactions and to easily perform a bifurcation analysis, which shows the qualitative dynamics of a model for a range of parameter values.</p> <p>Results</p> <p>We present Facile, a Perl command-line tool for analysing the dynamics of a systems biology model. Facile implements the law of mass action to automatically compile a biochemical network (written as, for example, <monospace>E + S <-> C</monospace>) into scripts for analytical analysis (Mathematica and Maple), for simulation (XPP and Matlab), and for bifurcation analysis (AUTO). Facile automatically identifies mass conservations and generates the reduced form of a model with the minimum number of independent variables. This form is essential for bifurcation analysis, and Facile produces a C version of the reduced model for AUTO.</p> <p>Conclusion</p> <p>Facile is a simple, yet powerful, tool that greatly accelerates analysis of the dynamics of a biochemical network. By acting at the command-line and because of its intuitive, text-based input, Facile is quick to learn and can be incorporated into larger programs or into automated tasks.</p

Termination, correctness and relative correctness

Over the last decade, research in verification and formal methods has been the subject of increased interest with the need of more secure and dependable software. At the heart of software dependability is the concept of software fault, defined in the literature as the adjudged or hypothesized cause of an error. This definition, which lacks precision, presents at least two challenges with regard to using formal methods: (1) Adjudging and hypothesizing are highly subjective human endeavors; (2) The concept of error is itself insufficiently defined, since it depends on a detailed characterization of correct system states at each stage of a computation (which is usually unavailable). In the process of defining what a software fault is, the concept of relative correctness, the property of a program to be more-correct than another with respect to a given specification, is discussed. Subsequently, a feature of a program is a fault (for a given specification) only because there exists an alternative to it that would make the program more-correct with respect to the specification. Furthermore, the implications and applications of relative correctness in various software engineering activities are explored. It is then illustrated that in many situations of software testing, fault removal and program repair, testing for relative correctness rather than absolute correctness leads to clearer conclusions and better outcomes. In particular, debugging without testing, a technique whereby, a fault can be removed from a program and the new program proven to be more-correct than the original, all without any testing (and its associated uncertainties/imperfections) is introduced. Given that there are orders of magnitude more incorrect programs than correct programs in use nowadays, this has the potential to expand the scope of proving methods significantly. Another technique, programming without refining, is also introduced. The most important advantage of program derivation by correctness enhancement is that it captures not only program construction from scratch, but also virtually all activities of software evolution. Given that nowadays most software is developed by evolving existing assets rather than producing new assets from scratch, the paradigm of software evolution by correctness enhancements stands to yield significant gains, if we can make it practical