Modelling soft error probability in firmware : a case study

This case study involves an analysis of rmware that controls explosions in mining operations. The purpose is to estimate the probability that external disruptive events (such as electro- magnetic interference) could drive the rmware into a state which results in an unintended explosion. Two probabilistic models are built, based on two possible types of disruptive events: a single spike of interference, and a burst of multiple spikes of interference. The models suggest that the system conforms to the IEC 61508 Safety Integrity Levels, even under very conservative assumptions of operation. The case study serves as a platform for future researchers to build on when modelling probabilistic soft errors in other contexts.http://www.orssa.org.za

Lists, taxonomies, lattices, thesauri and ontologies : paving a pathway through a terminological jungle

No abstract available.http://www.ergon-verlag.de/de/hb201

Extending backward polygon beam tracing of glossy scattering surfaces

Backward polygon beam tracing methods, that is beam tracing from the light source (L), are well suited to gather path coherency from specular (S) scattering surfaces. These methods are useful for modelling and efficiently simulating caustics on diffuse (D) surfaces; an effect due to LS+D transport paths. This paper generalizes backward polygon beam tracing to include a glossy (G) scattering surface. To this end the details of a beam tracing lumped model and implementation of L (S\G) D transport paths are presented. Although we limit the discussion to short transport paths, we show that backward beam tracing is faster than photon mapping by an order of magnitude for rendering caustics from glossy and specular surfaces.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1467-8659

Quality in software development : a pragmatic approach using metrics

As long as software has been produced, there have been e orts to strive for quality in software products. In order to understand quality in software products, researchers have built models of software quality that rely on metrics in an attempt to provide a quantitative view of software quality. The aim of these models is to provide software producers with the capability to de ne and evaluate metrics related to quality and use these metrics to improve the quality of the software they produce over time. The main disadvantage of these models is that they require e ort and resources to de ne and evaluate metrics from software projects. This article brie y describes some prominent models of software quality in the literature and continues to describe a new approach to gaining insight into quality in software development projects. A case study based on this new approach is described and results from the case study are discussed.http://www.journals.co.za/ej/ejour_comp.htmlam201

Weak factor automata : the failure of failure factor oracles?

In indexing of, and pattern matching on, DNA and text sequences, it is often important to represent all factors of a sequence. One e cient, compact representation is the factor oracle (FO). At the same time, any classical deterministic nite automaton (DFA) can be transformed to a so-called failure one (FDFA), which may use failure transitions to replace multiple symbol transitions, potentially yielding a more compact representation. We combine the two ideas and directly construct a failure factor oracle (FFO) from a given sequence, in contrast to ex post facto transformation to an FDFA. The algorithm is suitable for both short and long sequences. We empirically compared the resulting FFOs and FOs on number of transitions for many DNA sequences of lengths 4 - 512, showing gains of up to 10% in total number of transitions, with failure transitions also taking up less space than symbol transitions. The resulting FFOs can be used for indexing, as well as in a variant of the FO-using backward oracle matching algorithm. We discuss and classify this pattern matching algorithm in terms of the keyword pattern matching taxonomies of Watson, Cleophas and Zwaan. We also empirically compared the use of FOs and FFOs in such backward reading pattern matching algorithms, using both DNA and natural language (English) data sets. The results indicate that the decrease in pattern matching performance of an algorithm using an FFO instead of an FO may outweigh the gain in representation space by using an FFO instead of an FO.http://www.journals.co.za/ej/ejour_comp.htmlam201

Cross-impact analysis experimentation using two techniques to revise marginal probabilities of interdependent events

Cross-impact analysis relies on decision makers to provide marginal probability estimates of interdependent events. Generally, these have to be revised in order to ensure overall system coherency. This paper describes cross-impact analysis experimentation in which a Monte Carlo based approach and a difference equation approach, respectively, were used to revise these marginal probabilities. The objective of the study was to determine the consequences of such revisions on the expected impact rankings of these events. A cross-impact analysis system was developed and used to conduct the experiments. The experiments show that the impact ranking of interdependent events may indeed depend on the technique used for revising event marginal probabilities. Moreover, the Monte Carlo technique generates a world view closer to the one of the decision makers, while the world view generated by the difference equation technique differs from that of the decision makers.http://www.orssa.org.za

Perceptions of virtual globes, volunteered geographical information and spatial data infrastructures

The Internet has spawned the development of virtual communities or virtual social networks which generate and share information with one another, and with the public at large. Volunteered geographical information (VGI) refers to user-generated content that is made available as base data on public mapping web sites or as third party data overlaid on virtual globes such as Google Earth and NASA World Wind. Several attempts have been made to determine and categorise what motivates the contributors of VGI. However, while the contributors themselves might generally understand VGI, this is not necessarily the case amongst geographical information professionals at large. We used a questionnaire to explore this by gathering some data on the perceptions held by geographical information professionals of virtual globes, VGI and spatial data infrastructures (SDI). These perceptions are important because they influence how VGI and virtual globes will be used in future in the more formal SDI environments of official mapping agencies and other official custodians of spatial data. The questionnaire was administered at a meeting in Addis Ababa, Ethiopia, in April 2009 and at another in Ekurhuleni, South Africa, in June 2009. The results are reported on here. Some of the results confirm previous research, while others raise questions that warrant further research.http://pubs.cig-acsg.ca/journal/ci

Perceptions of virtual globes, volunteered geographical information and spatial data infrastructures

The Internet has spawned the development of virtual communities or virtual social networks which generate and share information with one another, and with the public at large. Volunteered geographical information (VGI) refers to user-generated content that is made available as base data on public mapping web sites or as third party data overlaid on virtual globes such as Google Earth and NASA World Wind. Several attempts have been made to determine and categorise what motivates the contributors of VGI. However, while the contributors themselves might generally understand VGI, this is not necessarily the case amongst geographical information professionals at large. We used a questionnaire to explore this by gathering some data on the perceptions held by geographical information professionals of virtual globes, VGI and spatial data infrastructures (SDI). These perceptions are important because they influence how VGI and virtual globes will be used in future in the more formal SDI environments of official mapping agencies and other official custodians of spatial data. The questionnaire was administered at a meeting in Addis Ababa, Ethiopia, in April 2009 and at another in Ekurhuleni, South Africa, in June 2009. The results are reported on here. Some of the results confirm previous research, while others raise questions that warrant further research.http://pubs.cig-acsg.ca/journal/ci

The South African Computer Journal : 1989 to 2010

The South African Computer Journal (SACJ), as the successor of the Quæstiones Informaticæ journal founded by Derek Henderson, is part of his heritage to South Africa. This brief historical sketch of SACJ outlines the role of various organisations and people that have been part of the journalʼs story, giving some insight into its financing and functioning, and pointing out highlights in its past editions