Distributed system software design paradigm with application tocomputer networks

A paradigm for the system and software design of distributed systems is presented with application to an actual large-scale computer network involving both local area networks and a wide area network. A number of design principles are offered with particular reference to how they can be applied to the design of distributed systems. The author's major point is an explanation of how to make design decisions about distributed systems in a way which will enhance maintainability and understandability of the software and, at the same time, result in good system performance. The aim is to recognize the implications for software quality of various decisions which must be made in the process of specifying a distributed system     

Application of Program Graphs and Complexity Analysis to Software Development and Testing

Several research studies have shown a strong relationship between program complexity, as measured by the structural properties of a program, and its error properties, as measured by number and types of errors and error detection and correction times. This research applies to: a) the setting of threshold values of complexity in software production in order to avoid undue difficulty with program debugging; b) the use of complexity as an index for allocating resources during the test phase of software development; c) the use of complexity for developing test strategies and the selection of test data. Application #c uses the directed graph representation of a program and its complexity measures to decompose the program into its basic constructs. The identification of the constructs serves to identify a) the components of the program which must be tested, and b) the selection of test data which are needed to exercise these components. Directed-graph properties which apply to program development and testing are defined; examples of the application of graph properties for program development and testing are given; the results of program complexity and error measurements are presented; and a procedure for complexity measurement and its use in programming and testing is summarized.     

Metrics for Mitigating Cybersecurity Threats to Networks

To achieve their full potential, networks must be secure as well as functional. With this in mind, the author identifies metrics designed to mitigate vulnerabilities to cyberattacks in networks that are key to the critical infrastructure of the US. He discusses both growth metrics — based on data obtained from the US National Institute of Standards and Technology and Department of Homeland Security vulnerability database — and metrics designed to mitigate the risk of security vulnerabilities in networks. If used together, these two types of metrics can help make networks more secure.     

Copolymerization and Dark Polymerization Studies for Photopolymerization of Novel Acrylic Monomers

The copolymerization behavior and the dark polymerization kinetics of highly reactive novel acrylic monomers were compared to traditional acrylate monomers. Copolymerization of thiol functionalities with novel acrylic monomers was characterized, and it was observed that the inclusion of secondary functionalities such as carbamates, carbonates, and cyclic carbonates, in acrylic monomers significantly alters the relative reactivity of the novel acrylates with thiols. While traditional aliphatic acrylates exhibited propagation to chain transfer ratios ranging between 0.8 (±0.1) and 1.5 (±0.2), the novel acrylates characterized by secondary functionalities exhibited much higher propagation to chain transfer ratios ranging from 2.8 (±0.2) to 4 (±0.2). In the dark polymerization studies, the kinetics of the novel acrylates were evaluated following cessation of the UV light. The novel acrylates exhibited extensive polymerization in the dark compared to most traditional acrylates and diacrylates. For instance, cyclic carbonate acrylate was observed to attain 35% additional conversion in the dark when the UV light was extinguished at 35% conversion, whereas traditional acrylates such as hexyl acrylate attained only 3% additional conversion when the UV light was extinguished at 35%, and a diacrylate such as HDDA attained 15% additional conversion when the UV light was extinguished at 40% conversion. Also, through choice of appropriate monomers, the dark polymerization studies were performed such that the polymerization rate was approximately the same at the point the light was extinguished for all these monomers. The copolymerization and dark polymerization studies support the hypothesis that the nature of the propagating species in the novel acrylates is altered as compared to traditional acrylic monomers and polymerizations.     

Validating metrics for ensuring Space Shuttle flight softwarequality

In this article, we cover the validation of software quality metrics for the Space Shuttle. Experiments with Space Shuttle flight software show that the Boolean OR discriminator function can successfully validate metrics for controlling and predicting quality. Further, we found that statement count and node count are the metrics most closely associated with the discrepancy reports count, and that with data smoothing their critical values can be used as predictors of software quality. We are continuing our research and comparing validated metrics with actual results in an attempt to determine whether the use of additional metrics provides sufficiently greater discriminative power to justify the increased inspection costs     

Controlling and predicting the quality of space shuttle software using metrics

Software quality metrics have potential for helping to assure the quality of software on large projects such as the Space Shuttle flight software. It is feasible to validate metrics for controlling and predicting software quality during design by validating metrics against a quality factor. Quality factors, like reliability, are of more interest to customers than metrics, like complexity. However quality factors cannot be collected until late in a project. Therefore the need arises to validate metrics, which developers can collect early in a project, against a quality factor. We investigate the feasibility of validating metrics for controlling and predicting quality on the Space Shuttle. The key to the approach is the use of validated metrics for early identification and resolution of quality problems.     

How to evaluate legacy system maintenance

Drawing on extensive data from the NASA Space Shuttle's guidance software, the author proposes a method for evaluating the effectiveness of legacy software maintenance efforts. He provides several formulas for tracking maintenance stability, defined as increasing functionality with decreasing failures over time, and offers data that supports their validity. He also provides tips for applying his formulas to different projects     

Software maintenance: The need for standardization

Hardware and software maintenance are contrasted. The key difference between the two-the ease with which software can be changed-leads to the need for managing software change. Standardization of software maintenance is proposed as a method for managing software change. A model of software maintenance is advanced as the foundation for standardizing software maintenance     

Representativeness models of systems: smart grid example

Given the great emphasis being placed on energy efficiency in contemporary society, in which the smart grid plays a prominent role, this is an opportune time to explore methodologies for appropriately representing system attributes. We suggest this is important for effective system development because the primary factor in correctly mapping between requirements and implementation is how representative the system design is of requirements. Since representativeness is an abstract term, it is imperative to identify ways to quantify it. We use several metrics. Among these is the priority of system elements (e.g., electric generator) in the set of elements, based on importance to system success. Secondly, fault tree analysis is employed to identify elements that operate in an unsafe state and the probabilities of reaching these unsafe states. Thirdly, state transition analysis provides traces of which elements are on the routes to unsafe states. These analyses provide the information needed to reduce element faults and failures on a priority basis.