Secure extensible languages, design of

The basic premise of this thesis is that extensible languages afford the user considerable power and flexibility. We argue that this flexibility can, and should, be provided in a secure and error-resistant manner, but that this objective is not realised in existing extensible languages. This thesis first investigates the nature of security in programming languages, building up a simple and informal theory of the design of secure languages, and relating this theory to the notions of structured programming and .transparency. We use this theory to build a conceptual model for a secure extensible language and its physical realisation. We show that existing extensible languages fail to meet the ideals of this model in total, and proceed to design an alternative and secure system which builds upon, but attempts to avoid the pitfalls of existing systems. We base this system on a string processing language (Snip) which is itself extensible. The remainder of this thesis discusses the design and implementation (based on an abstract machine, SAM) of this language

After Dark: Reading Canadian Literature in a Light-Polluted Age

A threat to nocturnal ecosystems and human health alike, light pollution is an unnecessary problem that comes at an enormous cost. The International Dark-Sky Association has recently estimated that the energy expended on light scatter alone is responsible for no less than twelve million tons of carbon dioxide and costs municipal governments at least $1 billion annually (“Economic Issues” 2). Emerging research also suggests that excessive artificial light at night may compromise melatonin production, a hormone that has been linked to the suppression of certain cancers (Stevens 28; Haim 32). As scotobiologists seek to solidify the connection between the disruption of circadian rhythms and compromised states of physical and mental well-being, the impetus to study the cultural and literary meaning of the night sky becomes all the more pressing. Drawing on a range of affect theorists, the findings of nocturnal ecologists, and ecocriticism’s call to memory and mindfulness, this dissertation assembles a diverse crew to consider the ways in which Canadian writers have chronicled the shift from natural darkness to artificial light. Too easily dismissed as nostalgic or sentimental, the desire to see the night sky make its return has never mattered more. To live in a time and a place where night never fully arrives is to know that the stars in a given volume of poetry may well outnumber those that remain visible in the sky. Literature itself has now drifted into an era of post-darkness, the world’s obsession with artificial light having ushered in a historical period that is, quite literally, after dark. For this reason, stories and poems that are rich in celestial allusions are worth studying because they place personal reflection, cosmological awareness, and empathetic witness in a century that has otherwise failed to appreciate the necessity of nocturnal environments the world over. Favouring lyrical persistence over nocturnal lament, the Nova Scotian poet Kenneth Leslie once set sail to “stubborn stars,” his imagination desiring those truths that only take shape in a sea of dark (1). Seventy-five years later, his finest sonnet still invites us to follow – headlong into the passages we find in search of better light to read by

Filtered Iterators For Safe and Robust Programs in RIFL

We present a new language construct, filtered iterators, for safe and robust input processing. Filtered iterators are designed to eliminate many common input-processing errors while enabling robust continued execution. The design is inspired by (a) observed common input-processing errors and (b) continued execution strategies that are implemented by developers fixing input validation errors. Filtered iterators decompose inputs into input units, atomically and automatically discarding units that trigger errors. Statistically significant results from a developer study highlight the difficulties that developers encounter when developing input-processing code using standard language constructs. These results also demonstrate the effectiveness of filtered iterators in eliminating many of these difficulties and enabling developers to produce safe and robust input-processing code

Symbolic execution and the testing of COBOL programs

The thesis is in two parts. Part one is a review of existing work in the area of software testing and more specifically symbolic execution. Part two is a description of the symbolic execution testing system for COBOL (SYM-BOL). Much of the work presented has been published or accepted for publication. Part one commences by introducing the aims of software testing and is followed by a review of the tools and techniques of software testing that have been developed over the past 25 years. A simple taxonomy of software testing techniques is given. One potentially powerful technique is symbolic execution. The principles of symbolic execution are described followed by the problems in applying symbolic execution. Part one is completed by a review of existing symbolic execution testing systems. No symbolic execution testing system has previously been built for a commercial data processing language such as COBOL. Part two commences by outlining the features of the SYM-BOL system and describes the user strategies that may be employed when using the system. The system generates an intermediate form in stages by transforming the source program into one that contains only a limited number of language constructs. Path selection can be automatic or undertaken by the user. In both cases the results of the symbolic execution already undertaken are available to the path selector to help reduce the likelihood of selecting an infeasible path. A description of how the Nag-library linear optimizer E04MBF is used for feasibility checking is given. Feasible solutions are turned into files of test cases. Simple assertions may be included in the source program which do not affect the normal execution of the software but which can be verified by inclusion in the symbolic execution

Software test and evaluation study phase I and II : survey and analysis

Issued as Final report, Project no. G-36-661 (continues G-36-636; includes A-2568

Analytical study of launch vehicle component level simulation, 26 March - 26 November 1965

Computer simulation feasibility study for Saturn launch vehicle and support equipmen

A comparison of time-sharing and batch processing through an analysis of programming errors

This thesis describes an experiment conducted to compare the response and performance of a programmer under the two current modes of program development: conversational time-sharing and batch processing. The research reported herein had two specific objectives. First to develop a procedure for identifying, classifying, and analyzing programming errors as a measure of performance, and secondly to ascertain experimentally if certain types of programming errors are more frequently occuring and more difficult to correct under conversational time-sharing than under the batch mode of processing

OK, computer? Understanding cybernetic personhood

Modern and Contemporary Studie

Modelling mechanisms of change in crop populations

Computer -based simulation models of changes occurring within crop populations when subjected to agents of phenotypic change, have been developed for use on commonly available personal computer equipment. As an underlying developmental principle, the models have been designed as general -case, mechanistic, stochastic models, in contrast to the predominantly empirically- derived, system -specific, deterministic (predictive) models currently available. A modelling methodology has evolved, to develop portable simulation models, written in high - level, general purpose code, allowing for use, modification and continued development by biologists with little requirement for computer programming expertise.The initial subject of these modelling activities was the simulation of the effects of selection and other agents of genetic change in crop populations, resulting in the computer model, PSELECT. Output from PSELECT, specifically phenotypic and genotypic response to phenotypic truncation selection, conformed to expectation, as defined by results from established analogue modelling work. Validation of the model by comparison of output with the results from an experimental -scale plant breeding exercise was less conclusive, and, owing to the fact that the genetic basis of the phenotypic characters used in the selection programme was insufficiently defined, the validation exercise provided only broad qualitative agreement with the model output. By virtue of the predominantly subjective nature of plant breeding programmes, the development of PSELECT resulted in a model of theoretical interest, but with little current practical application.Modelling techniques from the development of the PSELECT model were applied to the simulation of plant disease epidemics, where the modelled system is well characterised, and simulation modelling is an area of active research. The model SATSUMA, simulating the spatial and temporal development of diseases within crop populations, was developed. The model generates output which conforms to current epidemiological theory, and is compatible with contemporary methods of temporal and spatial analysis of crop disease epidemics. Temporal disease progress in the simulations was accurately described by variations of a generalised logistic model. Analysis of the spatial pattern of simulated epidemics by frequency distribution fitting or distance class methods was found to give good qualitative agreement with observed biological systems.The mechanistic nature of SATSUMA and its deliberate design as a general case model make it especially suitable for the investigation of component processes in a generalised plant disease epidemic, and valuable as an educational tool. Subject to validation against observational data, such models can be utilised as predictive tools by the incorporation of information (concerning crop species, pathogen etc.) specifically relevant to the modelled system. In addition to its educational use, SATSUMA has been used as research tool for the examination of the effect of spatial pattern of disease and disease incidence on the efficiency of sampling protocols and in parameterising a general theoretical model for describing the spatio -temporal development of plant diseases