Improving Automated Layout Techniques for the Production of Schematic Diagrams

This thesis explores techniques for the automated production of schematic diagrams, in particular those in the style of metro maps. Metro map style schematics are used across the world, typically to depict public transport networks, and therefore benefit from an innate level of user familiarity not found with most other data visualisation styles. Currently, this style of schematic is used infrequently due to the difficulties involved with creating an effective layout – there are no software tools to aid with the positioning of nodes and other features, resulting in schematics being produced by hand at great expense of time and effort. Automated schematic layout has been an active area of research for the past decade, and part of our work extends upon an effective current technique – multi-criteria hill climbing. We have implemented additional layout criteria and clustering techniques, as well as performance optimisations to improve the final results. Additionally, we ran a series of layouts whilst varying algorithm parameters in an attempt to identify patterns specific to map characteristics. This layout algorithm has been implemented into a custom-written piece of software running on the Android operating system. The software is targeted at tablet devices, using their touch-sensitive screens with a gesture recognition system to allow users to construct complex schematics using sequences of simple gestures. Following on from this, we present our work on a modified force-directed layout method capable of producing fast, high-quality, angular schematic layouts. Our method produces superior results to the previous octilinear force-directed layout method, and is capable of producing results comparable to many of the much slower current approaches. Using our force-directed layout method we then implemented a novel mental map preservation technique which aims to preserve node proximity relations during optimisation; we believe this approach provides a number of benefits over the the more common method of preserving absolute node positions. Finally, we performed a user study on our method to test the effect of varying levels of mental map preservation on diagram comprehension

Automatisches Zeichnen von Graphen für modellgetriebene Softwareentwicklung

As shown previously by Fuhrmann, there are several concepts for increasing the productivity of MDE by improving the practical handling of models. The automatic layout of graph-based models is a key enabler in this context. However, there is a striking contrast between the abundance of research results in the field of graph layout methods and the current state of graphical modeling tools, where only a tiny fraction of these results are ever adopted. This thesis aims to bridge this gap on three separate levels: specialized layout algorithms, configuration management, and software infrastructure. Regarding layout algorithms, here we focus on the layer-based approach. We examine its extension to include ports and hyperedges, which are essential features of certain kinds of graphs, e.g. data flow models. The main contribution is the handling of constraints on the positioning of ports, which is done mainly in the crossing minimization and edge routing phases. Hyperedges are represented with normal edges, simplifying their handling but introducing inaccuracies for counting crossings. A final extension discussed here is a sketch-driven approach for simple integration of user interactivity. An abstract layout is the selection of a layout algorithm with a mapping of its parameters to specific values. We discuss a new meta model allowing to specify the structure of a graph as well as its abstract layout and its concrete layout, i.e. positioning data computed by the layout algorithm. This forms a basis for efficient management of layout configurations. Furthermore, we investigate an evolutionary algorithm for searching the solution space of abstract layouts, taking readability criteria into account for evaluating solutions. The software infrastructure developed here targets the connection of arbitrary diagram viewers (front-ends) with arbitrary graph layout algorithms (back-ends). The main challenge is to find suitable abstractions that allow such generality and at the same time keep the complexity as low as possible. We discuss a possible realization based on the Eclipse platform, which is used by several modeling tools, e.g. the Graphical Modeling Framework. A web-based survey has been conducted among users of the layout infrastructure in order to evaluate to what extent the stated goals have been met. The overall feedback collected from this survey is very positive.Wie bereits von Fuhrmann gezeigt, kann die Produktivität modellgetriebener Softwareentwicklung durch zahlreiche Konzepte zur Verbesserung der praktischen Handhabung von Modellen erhöht werden. Dabei ist das automatische Layout graphenbasierter Modelle ein zentraler Schlüssel. Allerdings gibt es einen bemerkenswerten Kontrast zwischen der Fülle an Forschungsergebnissen im Bereich des Graphen-Layout und dem aktuellen Stand graphischer Modellierungswerkzeuge, bei denen nur ein kleiner Teil dieser Ergebnisse übernommen wird. Das Ziel dieser Arbeit ist diese Lücke auf drei separaten Ebenen zu überbrücken: spezialisierte Layout-Algorithmen, Verwaltung von Konfigurationen und Software-Infrastruktur. Im Bezug auf Layout-Algorithmen liegt der Schwerpunkt auf dem Layer-basierten Ansatz. Wir untersuchen dessen Erweiterung zur Unterstützung von Ports und Hyperkanten, was wesentliche Bestandteile bestimmter Arten von Graphen sind, z.B. Datenflussmodelle. Der Hauptbeitrag ist die Einbeziehung von Bedingungen für die Positionierung von Ports, vor allem während der Kreuzungsminimierung und der Kantenführungsphase. Hyperkanten werden durch normale Kanten repräsentiert, was deren Verarbeitung vereinfacht aber Ungenauigkeiten beim Zählen von Kreuzungen verursacht. Als letzte Erweiterung betrachten wir einen Sketch-basierten Ansatz für die einfache Integration von Nutzerinteraktivität. Ein abstraktes Layout ist die Auswahl eines Layout-Algorithmus zusammen mit einer Abbildung seiner Parameter auf konkrete Werte, während ein konkretes Layout Positionsdaten beschreibt, die von einem Algorithmus berechnet wurden. Wir diskutieren ein neues Metamodell, mit dem sowohl die Struktur als auch das abstrakte sowie das konkrete Layout eines Graphen spezifiziert werden kann. Dies bildet eine Grundlage für die effiziente Verwaltung von Layout-Konfigurationen. Zudem untersuchen wir einen evolutionären Algorithmus für die Suche im Lösungsraum abstrakter Layouts, wobei zur Bewertung von Lösungen Ästhetikkriterien ausgewertet werden. Die in dieser Arbeit entwickelte Software-Infrastruktur hat als Ziel, beliebige Graphen-basierte Diagramme (front-ends) mit beliebigen Layout-Algorithmen (back-ends) zu verbinden. Die größte Herausforderung dabei ist das Finden geeigneter Abstraktionen, die eine solche Allgemeingültigkeit erlauben und gleichzeitig die Komplexität so niedrig wie möglich halten. Wir betrachten eine mögliche Realisierung, die auf Eclipse basiert, eine von vielen Modellierungswerkzeugen verwendete Plattform. Eine Web-basierte Umfrage wurde unter Nutzern der Layout-Infrastruktur durchgeführt, um zu untersuchen inwieweit die gesteckten Ziele erfüllt worden sind. Die allgemeine Resonanz zu dieser Umfrage ist sehr positiv

Graph layout using subgraph isomorphisms

Today, graphs are used for many things. In engineering, graphs are used to design circuits in very large scale integration. In computer science, graphs are used in the representation of the structure of software. They show information such as the flow of data through the program (known as the data flow graph [1]) or the information about the calling sequence of programs (known as the call graph [145]). These graphs consist of many classes of graphs and may occupy a large area and involve a large number of vertices and edges. The manual layout of graphs is a tedious and error prone task. Algorithms for graph layout exist but tend to only produce a 'good' layout when they are applied to specific classes of small graphs. In this thesis, research is presented into a new automatic graph layout technique. Within many graphs, common structures exist. These are structures that produce 'good' layouts that are instantly recognisable and, when combined, can be used to improve the layout of the graphs. In this thesis common structures are given that are present in call graphs. A method of using subgraph isomorphism to detect these common structures is also presented. The method is known as the ANHOF method. This method is implemented in the ANHOF system, and is used to improve the layout of call graphs. The resulting layouts are an improvement over layouts from other algorithms because these common structures are evident and the number of edge crossings, clusters and aspect ratio are improved

Visualizing Set Relations and Cardinalities Using Venn and Euler Diagrams

In medicine, genetics, criminology and various other areas, Venn and Euler diagrams are used to visualize data set relations and their cardinalities. The data sets are represented by closed curves and the data set relationships are depicted by the overlaps between these curves. Both the sets and their intersections are easily visible as the closed curves are preattentively processed and form common regions that have a strong perceptual grouping effect. Besides set relations such as intersection, containment and disjointness, the cardinality of the sets and their intersections can also be depicted in the same diagram (referred to as area-proportional) through the size of the curves and their overlaps. Size is a preattentive feature and so similarities, differences and trends are easily identified. Thus, such diagrams facilitate data analysis and reasoning about the sets. However, drawing these diagrams manually is difficult, often impossible, and current automatic drawing methods do not always produce appropriate diagrams. This dissertation presents novel automatic drawing methods for different types of Euler diagrams and a user study of how such diagrams can help probabilistic judgement. The main drawing algorithms are: eulerForce, which uses a force-directed approach to lay out Euler diagrams; eulerAPE, which draws area-proportional Venn diagrams with ellipses. The user study evaluated the effectiveness of area- proportional Euler diagrams, glyph representations, Euler diagrams with glyphs and text+visualization formats for Bayesian reasoning, and a method eulerGlyphs was devised to automatically and accurately draw the assessed visualizations for any Bayesian problem. Additionally, analytic algorithms that instantaneously compute the overlapping areas of three general intersecting ellipses are provided, together with an evaluation of the effectiveness of ellipses in drawing accurate area-proportional Venn diagrams for 3-set data and the characteristics of the data that can be depicted accurately with ellipses

Runtime MPI Correctness Checking with a Scalable Tools Infrastructure

Increasing computational demand of simulations motivates the use of parallel computing systems. At the same time, this parallelism poses challenges to application developers. The Message Passing Interface (MPI) is a de-facto standard for distributed memory programming in high performance computing. However, its use also enables complex parallel programing errors such as races, communication errors, and deadlocks. Automatic tools can assist application developers in the detection and removal of such errors. This thesis considers tools that detect such errors during an application run and advances them towards a combination of both precise checks (neither false positives nor false negatives) and scalability. This includes novel hierarchical checks that provide scalability, as well as a formal basis for a distributed deadlock detection approach. At the same time, the development of parallel runtime tools is challenging and time consuming, especially if scalability and portability are key design goals. Current tool development projects often create similar tool components, while component reuse remains low. To provide a perspective towards more efficient tool development, which simplifies scalable implementations, component reuse, and tool integration, this thesis proposes an abstraction for a parallel tools infrastructure along with a prototype implementation. This abstraction overcomes the use of multiple interfaces for different types of tool functionality, which limit flexible component reuse. Thus, this thesis advances runtime error detection tools and uses their redesign and their increased scalability requirements to apply and evaluate a novel tool infrastructure abstraction. The new abstraction ultimately allows developers to focus on their tool functionality, rather than on developing or integrating common tool components. The use of such an abstraction in wide ranges of parallel runtime tool development projects could greatly increase component reuse. Thus, decreasing tool development time and cost. An application study with up to 16,384 application processes demonstrates the applicability of both the proposed runtime correctness concepts and of the proposed tools infrastructure

Adaptive Methods for Robust Document Image Understanding

A vast amount of digital document material is continuously being produced as part of major digitization efforts around the world. In this context, generic and efficient automatic solutions for document image understanding represent a stringent necessity. We propose a generic framework for document image understanding systems, usable for practically any document types available in digital form. Following the introduced workflow, we shift our attention to each of the following processing stages in turn: quality assurance, image enhancement, color reduction and binarization, skew and orientation detection, page segmentation and logical layout analysis. We review the state of the art in each area, identify current defficiencies, point out promising directions and give specific guidelines for future investigation. We address some of the identified issues by means of novel algorithmic solutions putting special focus on generality, computational efficiency and the exploitation of all available sources of information. More specifically, we introduce the following original methods: a fully automatic detection of color reference targets in digitized material, accurate foreground extraction from color historical documents, font enhancement for hot metal typesetted prints, a theoretically optimal solution for the document binarization problem from both computational complexity- and threshold selection point of view, a layout-independent skew and orientation detection, a robust and versatile page segmentation method, a semi-automatic front page detection algorithm and a complete framework for article segmentation in periodical publications. The proposed methods are experimentally evaluated on large datasets consisting of real-life heterogeneous document scans. The obtained results show that a document understanding system combining these modules is able to robustly process a wide variety of documents with good overall accuracy