Contributions in Merlin

This book constitutes the thoroughly refereed post-workshop proceedings of the Workshop on Controlled Natural Language, CNL 2009, held in Marettimo Island, Italy, in June 2009. The 16 revised full papers presented together with 1 invited lecture were carefully reviewed and selected during two rounds of reviewing and improvement from 31 initial submissions. The papers are roughly divided into the two groups language aspects and tools and applications. Note that some papers fall actually into both groups: using a controlled natural language in an application domain often requires domain-specific language features.

Employee fraud in financial institutions is a considerable monetary and reputational risk. Studies state that this type of fraud is typically detected by a tip, in the worst case from affected customers, which is fatal in terms of reputation. Consequently, there is a high motivation to improve analytic detection. We analyze the problem of client advisor fraud in a major financial institution and find that it differs substantially from other types of fraud. However, internal fraud at the employee level receives little attention in research. In this thesis, we provide an overview of fraud detection research with the focus on implicit assumptions and applicability. We propose a decision framework to find adequate fraud detection approaches for real world problems based on a number of defined characteristics. By applying the decision framework to the problem setting we met at Alphafin the chosen approach is motivated. The proposed system consists of a detection component and a visualization component. A number of implementations for the detection component with a focus on tempo-relational pattern matching is discussed. The visualization component, which was converted to productive software at Alphafin in the course of the collaboration, is introduced. On the basis of three case studies we demonstrate the potential of the proposed system and discuss findings and possible extensions for further refinements.

In den letzten Jahren haben partikelbasierte Methoden zur Simulation von Gasen und Flüssigkeiten in der Computer Graphik an Wichtigkeit gewonnen. Dies da die Repräsentation durch Partikel die Behandlung von freien Oberflächen, Spritzer, Tropfen und komplexen Interaktionen zwischen Objekten erleichtert. Partikelbasierte Methoden weisen jedoch auch Nachteile auf welche das physikalische Verhalten eines Fluids und somit das resultierende visuelle Resultat beeinträchtigen. Obwohl diese Probleme in sozusagen allen partikelbasierten Modellen präsent sind, konzentriert sich diese Dissertation auf die Hauptprobleme der Methode Smoothed Particle Hydrodynamics (SPH). Diese Dissertation beginnt mit einer Einführung in die SPH Methode und erklärt die Schwierigkeit inkompressible Flüssigkeiten zu simulieren. Im Grundmodell von SPH werden Flüssigkeiten durch kompressible Fluide approximiert was zu ungewollten Kompressionsartefakten führt. Obwohl Inkompressibilität erzwungen werden kann, repräsentiert dies den berechenmässig teuersten Teil der Methode, was der Grund ist warum SPH und partikelbasierte Methoden im Allgemeinen weniger geeignet sind um photorealistische Animation von Wasser zu erstellen. In dieser Arbeit präsentieren wir ein neues, inkompressibles Verfahren basierend auf SPH welche Inkompressibilität durch eine Prädiktor-Korrektor Methode erzwingt. Dabei werden die Informationen uber Dichteabweichungen aktiv durch das Fluid propagiert und Druckwerte angepasst, solange bis die Dichtewerte der Partikel einheitlich sind. Mit diesem Ansatz können die Berechnungskosten per Simulationsschritt niedrig gehalten und gleichzeitig ein grosser Simulationszeitschritt verwendet werden. Danach gehen wir auf die Probleme ein welche an den Zwischenflächen von mehreren Fluiden mit unterschiedlicher Dichte entstehen, sowie zwischen Fluiden und festen Objekten. Bei der Simulation von mehreren Fluiden mit dem SPH Grundmodell können Artefakte an der Zwischenfläche beobachtet werden, welche das Verhalten der Fluide negativ beeinflusst. Diese Artefakte sind unphysikalische Oberflächenspannungen sowie numerische Instabilitäten. Diese Dissertation präsentiert ein adaptiertes SPH Modell welches Diskontinuitiäten an den Zwischenflächen von mehreren Fluiden korrekt behandelt und dadurch die Probleme des Grundmodells vermeidet. Des Weiteren prä sentiert diese Arbeit ein einheitliches Modell für die Simulation von Fluiden und festen Objekten um die Interaktion zwischen unterschiedlichen Materialien zu erleichtern. In unserem Modell sind Flüssigkeiten und Gase sowie starre und elastische Körper durch Partikel repräsentiert welche Attribute mit den Objekteigenschaften tragen. Durch das Andern der Attribute können Effekte wie Schmelzen und Erstarren, sowie Vereinigung und Trennung von Objektteilen mit niedrigem Aufwand simuliert werden. Zum Abschluss stellen wir eine neue, effiziente Partikel-Verfeinerungsmethode vor um eine höhere visuelle Qualität beim Rendering von Echtzeit-Flüssigkeiten zu erreichen. Als Ausgangspunkt verwendet unsere Methode die Punktmenge der Simulation und fügt uniform neue Punkte hinzu wobei Oberflächenstrukturen akkurat beibehalten werden. Eine weitere Schwierigkeit von Partikelmethoden ist die Rekonstruktion von glatten Oberflächen. Um dies zu erreichen verwenden wir eine neue Methode, welche den Partikelschwerpunkt der Nachbarschaft bei der Rekonstruktion verwendet, und wir zeigen wie Artefakte in konkaven Regionen erfolgreich vermieden werden können. Particle-based fluid simulations have become popular in computer graphics due to their natural ability to handle free surfaces and interfaces, splashes and droplets, as well as interaction with complex boundaries. However, particle methods have some disadvantageous properties degrading the physical behavior of a simulated fluid and thus the resulting visual quality. Although these problems are present in almost any particle-based fluid solver, this dissertation addresses some of the major problems of the Lagrangian method Smoothed Particle Hydrodynamics (SPH). This thesis starts by reviewing the standard SPH model and its difficulties to satisfy the incompressibility condition. In the standard model, liquids are typically approximated by compressible fluids where pressures are determined by an equation of state, resulting in undesired compression artifacts. Although incompressibility can be enforced, it represents the most expensive part of the whole simulation process and thus renders particle methods less attractive for high quality and photorealistic water animations. In this thesis, we present a novel, incompressible fluid simulation method based on SPH. In our method, incompressibility is enforced by using a prediction-correction scheme to determine the particle pressures. For this, the information about density fluctuations is actively propagated through the fluid and pressure values are updated until the targeted density is sat- isfied. With this approach, the costs per simulation update step can be held low while still being able to use large time steps in the simulation. Next, we shift our attention to the problem of complex interactions between multiple different fluids as well as between fluids and solids. We first focus on the artifacts caused by standard SPH when simulating multiple fluids with high-density ratios. In the standard model, the smoothed quantities of particles near the fluid interface show falsified values and the physical behavior is severely affected, especially if density ratios become large. The artifacts include spurious and unphysical interface tension as well as severe numerical instabilities. In this thesis, we derive a formulation that can handle discontinuities at interfaces of multiple fluids correctly and thus avoids the problems present in standard SPH. With our concepts, an animator has full control over the behavior of multiple interacting fluids. Furthermore, we propose to represent both, fluids and solids, by particles, facilitating the interaction between the different object types. We present a unified simulation model for fluids, rigid, and elastic objects, and show how phase transitions can be modeled by only changing the attribute values of the underlying particles. New effects like merging and splitting due to melting and solidification are demonstrated, and we show that our model is able to handle coarsely sampled and even coplanar particle configurations without further treatment. Finally, we present a novel point refinement method to achieve a higher visual quality of low-resolution fluids. We introduce new algorithms to efficiently upsample an initial point set given by the physical computation. Our method features the ability to accurately preserve surface details and to reach a uniform point distribution. Another challenge is to reconstruct smooth surfaces from the particles. The visualized fluids typically suffer from bumpy surfaces related to the irregular particle distribution. In order to achieve smooth surfaces, this thesis introduces a new surface reconstruction technique based on the center of mass of the particle neighborhood. We show how artifacts in concave regions can be avoided by considering the movement of the center of mass.

It is widely agreed that amputees have to rely on visual input to monitor and control the position of the prosthesis while reaching and grasping because of the lack of proprioceptive feedback. Therefore, visual information has been a prerequisite for prosthetic hand biofeedback studies. This is why, the underlying characteristics of other artificial feedback methods used to this day, such as auditive, electro-tactile, or vibro-tactile feedback, has not been clearly explored. The purpose of this paper is to explore whether it is possible to use audio feedback alone to convey more than one independent variable (multichannel) simultaneously, without relying on the vision, to improve the learning of a new perceptions, in this case, to learn and understand the artificial proprioception of a prosthetic hand while reaching. Experiments are conducted to determine whether the audio signals could be used as a multi-variable dynamical sensory substitution in reaching movements without relying on the visual input. Two different groups are tested, the first one uses only audio information and the second one uses only visual information to convey computer-simulated trajectories of two fingers.

One of the most important decisions researchers face when analyzing software systems is the choice of a proper data analysis/exchange format. In this paper, we present EvoOnt, a set of software ontologies and data exchange formats based on OWL. EvoOnt models software design, release history information, and bug-tracking meta-data. Since OWL describes the semantics of the data, EvoOnt (1) is easily extendible, (2) can be processed with many existing tools, and (3) allows to derive assertions through its inherent Description Logic reasoning capabilities. The contribution of this paper is that it introduces a novel software evolution ontology that vastly simplifies typical software evolution analysis tasks. In detail, we show the usefulness of EvoOnt by repeating selected software evolution and analysis experiments from the 2004-2007 Mining Software Repositories Workshops (MSR). We demonstrate that if the data used for analysis were available in EvoOnt then the analyses in 75% of the papers at MSR could be reduced to one or at most two simple queries within off-the-shelf SPARQL tools. In addition, we present how the inherent capabilities of the Semantic Web have the potential of enabling new tasks that have not yet been addressed by software evolution researchers, e.g., due to the complexities of the data integration.

Empirical studies of software defects rely on links between bug databases and program code repositories. This linkage is typically based on bug-fixes identified in developer-entered commit logs. Unfortunately, developers do not always report which commits perform bug-fixes. Prior work suggests that such links can be a biased sample of the entire population of fixed bugs. The validity of statistical hypotheses-testing based on linked data could well be affected by bias. Given the wide use of linked defect data, it is vital to gauge the nature and extent of the bias, and try to develop testable theories and models of the bias. To do this, we must establish ground truth: manually analyze a complete version history corpus, and nail down those commits that fix defects, and those that do not. This is a diffcult task, requiring an expert to compare versions, analyze changes, find related bugs in the bug database, reverse-engineer missing links, and finally record their work for use later. This effort must be repeated for hundreds of commits to obtain a useful sample of reported and unreported bug-fix commits. We make several contributions. First, we present Linkster, a tool to facilitate link reverse-engineering. Second, we evaluate this tool, engaging a core developer of the Apache HTTP web server project to exhaustively annotate 493 commits that occurred during a six week period. Finally, we analyze this comprehensive data set, showing that there are serious and consequential problems in the data.

Software engineering process information extracted from version control systems and bug tracking databases are widely used in empirical software engineering. In prior work, we showed that these data are plagued by quality deficiencies, which vary in its characteristics across projects. In addition, we showed that those deficiencies in the form of bias do impact the results of studies in empirical software engineering. While these findings affect software engineering researchers the impact on practitioners has not yet been substantiated. In this paper we, therefore, explore (i) if the process data quality and characteristics have an influence on the bug fixing process and (ii) if the process quality as measured by the process data has an influence on the product (i.e., software) quality. Specifically, we analyze six Open Source as well as two Closed Source projects and show that process data quality and characteristics have an impact on the bug fixing process: the high rate of empty commit messages in Eclipse, for example, correlates with the bug report quality. We also show that the product quality -- measured by number of bugs reported -- is affected by process data quality measures. These findings have the potential to prompt practitioners to increase the quality of their software process and its associated data quality.