We describe an empirical evaluation of a visualization approach based on a 3D city metaphor, implemented in a tool called CodeCity. We designed the controlled experiment based on a set of lessons extracted from the current body of research and perfected it during a preliminary pilot phase. We then conducted the experiment in four locations across three countries over a period of four months,...
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Middleware-based database replication protocols require few or no changes in the database engine. As a consequence, they are more portable and flexible than kernel-based protocols, but have coarser-grain information about transaction access data, resulting in reduced concurrency and increased aborts. This paper proposes conflict-aware load-balancing techniques to increase the concurrency and...
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In: Innovative Minds (Information Systems Security Association - ISSA 2008), Johannesburg, South Africa, July 2008, 2008, p. -
The threats and intrusions in IT systems can basically be compared to human diseases with the difference that the human body has an effective way to deal with them, what still need to be designed for IT systems. The human immune system (HIS) can detect and defend against yet unseen intruders, is distributed, adaptive and multilayered to name only a few of its features. Our immune system...
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In: Journal of Computational Chemistry, 2008, vol. 29, no. 2, p. 306 - 311
A new program called pyVib has been developed as a tool for the analysis of Gaussian (Gaussian 03, Gaussian Inc., Pittsburgh, PA) outputs of vibrational absorption (IR), Raman as well as vibrational optical activity (VOA) spectra calculations. This program has been designed to help the computational chemistry practitioner in the task of analyzing and visualizing molecular vibrations and cross...
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This paper tackles the problem of structural integration testing of stateful classes. Previous work on structural testing of object-oriented software exploits data flow analysis to derive test requirements for class testing and defines contextual def-use associations to characterize inter-method relations. Non-contextual data flow testing of classes works well for unit testing, but not for...
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In this paper, we study the atomic broadcast and multicast problems, two fundamental abstractions for building fault-tolerant systems. As opposed to atomic broadcast, atomic multicast allows messages to be addressed to a subset of the processes in the system, each message possibly being multicast to a different subset. We require atomic multicast algorithms to be genuine, i.e., only processes...
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Software development practice still relies on the notion that programming is equivalent to editing text. This view is also supported by mainstream versioning systems, such as CVS and SubVersion, which are excellent at versioning text files. We argue that programming = text editing may have been true years ago, but nowadays we construct complex systems by changing them piecemeal. However, despite...
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We describe the implementation and experimental evaluation of a fault-tolerant leader election service for dynamic systems. Intuitively, distributed applications can use this service to elect and maintain an operational leader for any group of processes which may dynamically change. If the leader of a group crashes, is temporarily disconnected, or voluntarily leaves the group, the service...
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In: Lecture Notes in Computer Science, 2006, vol. 4209, p. 316-328
As part of a Distributed Information Retrieval system a description of each remote information resource, archive or repository is usually stored centrally in order to facilitate resource selection. The acquisition of precise resource descriptions is therefore an important phase in Distributed Information Retrieval, as the quality of such representations will impact on selection accuracy, and...
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In: The European Physical Journal: Applied Physics, 2006, vol. 33, p. 221-224
For physical processes which express themselves as a frequency, for example magnetic field measurements using optically-pumped alkali-vapor magnetometers, the precise extraction of the frequency from the noisy signal is a classical problem. We describe herein a frequency measurement system based on an inexpensive commercially available computer sound card coupled with a software single-tone...
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