Should we try to measure software quality attributes directly?

Most external software quality attributes are conceptually subjective. For example, maintainability is an external software quality attribute, and it is subjective because interpersonally agreed definitions for the attribute include the phrase ‘the ease with which maintenance tasks can be performed’. Subjectivity clearly makes measurement of the attributes and validation of prediction systems for the attributes problematic. In fact, in spite of the definitions, few statistically valid attempts at determining the predictive capability of prediction systems for external quality attributes have been published. When validations have been attempted, one approach used is to ask experts to indicate if the values provided by the prediction system informally agree with the experts’ intuition. These attempts are undertaken without determining, independently of the prediction system, whether the experts are capable of direct consistent measurement of the attribute. Hence, a statistically valid and unbiased estimate of the predictive capability of the prediction system cannot be obtained (because the experts’ measurement process is not independent of the prediction system’s values). In this paper, it is argued that the problem of subjective measurement of quality attributes should not be ignored if quality is to be introduced into software in a controlled way. Further, it is argued that direct measurement of quality attributes should be encouraged and that in fact such measurement can be quantified to establish consistency using an existing approach. However, the approach needs to be made more accessible to promote its use. In so doing, it would be possible to decide whether consistent independent estimates of the true values of software quality attributes can be assigned and prediction systems for quality attributes developed.

Comparison of functional performance of a soldier in full chemical and biological protection versus battle dress

The comparison of functional performance between a soldier wearing a chemical and biological (CB) protective equipment and an ordinary battle dress (BD) was conducted at Protechnik's facilities and Jozini–South Africa. The basis of the comparison was that CB protective equipment causes compatibility problems such as mobility and clearance, and that these factors would affect the soldier when performing various activities. Sixteen obstacle courses were erected to simulate a range of functions normally performed by an infantry soldier. Time taken by each soldier to complete a variety of motions and obstacle clearance activities was recorded. It was found that the CB protective equipment interfered with the soldier's performance. The soldier's movements were observed to be restricted and abnormal. The time taken to complete similar activities was longer when wearing the CB protective equipment than ordinary BD.

Relevance to industry

To determine the effect of protective equipment on functional performance.     

Chipping

Networks dominate today’s computing environment and commercial technical protection is lagging behind attack technology. As a result, protection programme success depends more on prudent management decisions than on the selection of technical safeguards. Managing Network Security takes a management view of protection and seeks to reconcile the need for security with the limitations of technology.     

Why everything keeps failing

Networks dominate today's computing landscape and commercial technical protection is lagging behind attack technology. As a result, protection programme success depends more on prudent management decisions than on the selection of technical safeguards. Managing Network Security takes a management view of protection and seeks to reconcile the need for security with the limitations of technology.     

Optimal structural topologies with transmissible loads

In optimal topological design of structures one obtains the configuration of optimal structures when the design domain, the displacement boundary conditions and the applied loads are specified. In the optimal structure one often notices a marked difference between the main bearing structure and the load transfer zones. The latter are composed of relatively light elements the exact nature of which is not always very distinct. The main purpose of this paper is to allow the main bearing part of the structure to emerge. Moreover the actual location of the load along its line of action is not always a design requirement. In order to include this relaxed condition regarding the loading position the concept of transmissible or sliding forces is introduced in topological design of structures. A transmissible force is a force of given magnitude and direction which can be applied at any point along the line of action of the force. The optimization formulation is similar to standard topological design procedure in addition to the condition of transmissability of the forces. It is shown that this condition reduces to an equal displacement constraint along the line of action of the forces. The method is illustrated by typical structural examples. It is observed that this numerical method produces indeed crisp images of the main structural components, unblurred by the secondary load transfer elements. It is also indicated that many results are often replicas of Prager structures which were previously obtained by analytical methods. Received March 3, 1999     

Effects of temperature on a.c. magnetostriction in grain-oriented silicon-iron

The a.c. magnetostriction of conventional grain-oriented 3 1/4% silicon-iron and more highly oriented silicon-iron has been measured from room temperature up to the Curie point using high temperature strain gauges. Curves of magnetostriction plotted against flux density showed that a definite change in the magnetization process occurred at about 300° C extending to 400° C for both types of material. This was considered to be due to the onset of magnetic annealing, considerably modified by the effect of the coating on the materials. From the experimental results the magnetostriction constant ₁₀₀ has been calculated using a predicted domain structure and was found to agree well with single crystal values apart from within the 300 to 400° C region.     

Macsyma: A personal history

The Macsyma system arose out of research on mathematical software in the AI group at MIT in the 1960s. Algorithm development in symbolic integration and simplification arose out of the interest of people, such as the author, who were also mathematics students. The later development of algorithms for the GCD of sparse polynomials, for example, arose out of the needs of our user community. During various times in the 1970s the computer on which Macsyma ran was one of the most popular nodes on the ARPANET. We discuss the attempts in the late 70s and the 80s to develop Macsyma systems that ran on popular computer architectures. Finally, we discuss the impact of the fundamental ideas in Macsyma on the author’s current research on large scale engineering and socio-technical systems.     

Learning invariance from natural images inspired by observations in the primary visual cortex

The human visual system has the remarkable ability to largely recognize objects invariant of their position, rotation, and scale. A good interpretation of neurobiological findings involves a computational model that simulates signal processing of the visual cortex. In part, this is likely achieved step by step from early to late areas of visual perception. While several algorithms have been proposed for learning feature detectors, only few studies at hand cover the issue of biologically plausible learning of such invariance. In this study, a set of Hebbian learning rules based on calcium dynamics and homeostatic regulations of single neurons is proposed. Their performance is verified within a simple model of the primary visual cortex to learn so-called complex cells, based on a sequence of static images. As a result, the learned complex-cell responses are largely invariant to phase and position.