IADIS-INTERNATIONAL JOURNAL ON COMPUTER SCIENCE AND INFORMATION SYSTEMS

17-31

Authors: Sujay Muramalla, Ragaad AlTarawneh, Shah Rukh Humayoun, Ricarda Moses, Sven Panis and Achim Ebert

Space-filling techniques have been used in the information visualization field as an alternative to the conventional node-link layouts for intuitively showing large hierarchies in less space. Different space filling layouts have been designed, developed and evaluated; however, much less effort have been made to look into how layout can impact user task performance on hierarchical data structures. In this paper, we focus on the impact of layout on user task performance by conducting evaluation studies for two common space-filling layout structures, the Sunburst (radial) layout and the Icicle (rectangular) layout. In our studies, users performed eight search-based tasks on files and directories in the resulting visualizations, first in a controlled environment and subsequently in an online environment. We focused on deriving user performance metrics with regard to effectiveness, efficiency, and user acceptance. Results demonstrate a mixed view of task performance and preference with both layouts, e.g., users performed better with the Icicle layout while they preferred the Sunburst layout for visual aesthetics. We further analyzed the impact of layout on the performance dynamics in terms of response times and accuracy using event history analysis (EHA) in the control study setting. The EHA results revealed clear differences in response tendencies even though no differences existed in mean response times for most of the tasks. It also clearly showed that participants performed more efficiently with the directory comparison tasks than the file comparison tasks. Overall, through these studies we were able to derive causal relationships between the layout and the user’s task performance while interacting with hierarchical data structures.

50-64

Authors: Hardy Pundt

Spatial decision making often requires the consideration of huge datasets from a great variety of sectors. For the achievement of decision that are accepted by as many actors as possible it is indispensable to consider all relevant fields, and contexts. However, if the goal of a project is ill defined or broadly scoped, it can be hard to identify all relevant actors and overview whether their different goals, perceptions and ideas of how a place, a landscape, a village or city should develop in the future, can be integrated. Actors recognize problems necessarily within their specific context. The idea of a holistic approach to decision making is to consider possibly all relevant contexts, in which a spatial problem is embedded. This should lead to qualitatively high and sustainable decisions because the ignorance of specific contextual information can lead to unsatisfying, in the worst case harmful results. The problem as such is not new, but this paper argues not from a perspective of human communication. It raises the question, whether applications can support a holistic approach in spatial decision making by extending decision systems with functionalities to integrate context-information automatically.

86-101

Authors: Duarte Pousa and José Rufino

System Virtualization has become a fundamental IT tool, whether it is type-2/hosted virtualization, mostly exploited by end-users in their personal computers, or type-1/bare metal, well established in IT departments and thoroughly used in modern datacenters as the very foundation of cloud computing. Though bare metal virtualization is meant to be deployed on server-grade hardware (for performance, stability and reliability reasons), properly configured desktop-class systems or workstations are often used as virtualization servers, due to their attractive performance/cost ratio. This paper presents the results of a study conducted on commodity virtualization servers, aiming to assess the performance of a representative set of the type-1 platforms mostly in use today: VMware ESXi, Citrix XenServer, Microsoft Hyper-V, oVirt and Proxmox. Hypervisor performance is indirectly measured through synthetic benchmarks performed on Windows 10 LTSB and Linux Ubuntu Server 16.04 guests: PassMark for Windows, UnixBench for Linux, and the cross-platform Flexible I/O Tester and iPerf3 benchmarks. The evaluation results may be used to guide the choice of the best type-1 platform (performance-wise), depending on the predominant guest OS, the performance patterns (CPUbound, IO-bound, or balanced) of that OS, its storage type (local/remote) and the required network-level performance.

115-132

Authors: Samuel Mann

The premise of Computing Education for Sustainability (CEfS) is examined. CEfS is described as a leverage discipline, where the handprint is much larger than the footprint. The potential of this leverage is described and the development of the field explored. Unfortunately CEfS is found not to be making sufficient impact in terms of a contribution at scale to system change actions resulting in restorative socio-ecological transformation. A transformation mindset is described that provides a lens for considering the role of CEfS and what might be done about it. Three inspirations are described - a case study of a learner with an ambitious change aspiration, a values-driven business, and an alternative approach to education: work-based professional practice education. These lead to consideration of implications, which while not exhaustive, are intended to provoke debate about the nature of computing education for sustainability.

148-165

Authors: Pavel Tarasov and Hitesh Tewari

Voting systems have been around for hundreds of years and despite different views on their integrity, have always been deemed secure with some fundamental security and anonymity principles. Numerous electronic systems have been proposed and implemented but some suspicion has been raised regarding the integrity of elections due to detected security vulnerabilities within these systems. Electronic voting, to be successful, requires a more transparent and secure approach, than is offered by current protocols. The approach presented in this paper involves a protocol developed on blockchain technology. The underlying technology used in the voting system is a payment scheme, which offers anonymity of transactions, a trait not seen in blockchain protocols to date. The proposed protocol offers anonymity of voter transactions, while keeping the transactions private, and the election transparent and secure. The underlying payment protocol has not been modified in any way, the voting protocol merely offers an alternative use case.