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Visone Software for the Analysis and Visualization of Social Networks

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Visone Software for the Analysis and Visualization of Social Networks visone Software for the Analysis and Visualization of Social Networks zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften der Fakult¨atf¨urInformatik der Universit¨atFridericiana zu Karlsruhe (TH) genehmigte Dissertation von Michael Baur aus Ravensburg Tag der m¨undlichenPr¨ufung: 13. November 2008 Erste Gutachterin: Frau Prof. Dr. Dorothea Wagner Zweiter Gutachter: Herr Prof. Dr. Ulrik Brandes Contents 1 Zusammenfassung 7 1.1 Uberblick¨ . .7 1.2 Grundlagen von visone . .8 1.3 Analyse . .8 1.4 Visualisierung . .9 1.5 Weitere Funktionen . 11 2 Motivation 13 3 visone Basics 17 3.1 Graph Theory . 18 3.2 Network Model . 21 3.2.1 Direction . 21 3.2.2 Confirmation . 22 3.2.3 Weights and Attributes . 23 3.2.4 Data Representation . 24 3.3 visone User Interface . 24 3.3.1 Main Window . 25 3.3.2 Graphical Properties and Templates . 27 3.3.3 Geometric Transformations . 27 3.3.4 Selections . 28 3.3.5 Edge Transformations . 29 3.3.6 Attributes . 31 4 Analysis 33 4.1 Characteristics of Input Data . 33 4.2 Size of the Graph . 35 4.3 Centrality . 35 4 Contents 4.3.1 Normalization . 36 4.3.2 Degree . 36 4.3.3 Distance . 37 4.3.4 Shortest Paths . 38 4.3.5 Shortest-Path Edge Centralities . 40 4.3.6 Current-Flow . 41 4.3.7 Feedback . 43 4.4 Neighborhood Density . 47 4.5 Cohesiveness . 49 4.5.1 k-core . 49 4.5.2 Cliques & Co . 50 4.6 Connectedness . 51 4.7 Clustering . 52 4.7.1 Quality Measures . 53 4.7.2 Clustering Methods . 56 4.7.3 Conclusion . 58 4.8 Network Statistics . 59 5 General Graph Layout 63 5.1 Preliminaries . 64 5.2 Criteria of Good Layouts . 64 5.3 Random Layout . 65 5.4 Circular Layout . 65 5.5 Force-Directed Layouts . 66 5.5.1 Classical Force-Directed Layout . 68 5.5.2 Classical MDS . 69 5.5.3 Stress Majorization . 70 5.5.4 Conclusion . 72 5.6 Spectral Layout . 72 6 Analytic Visualization 75 6.1 Basic Visualizations . 76 6.1.1 Sizes . 76 6.1.2 Colors . 77 Contents 5 6.1.3 Labels . 80 6.1.4 z-Coordinate . 81 6.2 Radial Visualization . 81 6.2.1 Layout Algorithm . 82 6.2.2 Final Placement . 83 6.2.3 Confirmation . 83 6.2.4 Scale . 85 6.2.5 User Interaction . 85 6.2.6 Final Remarks . 86 6.3 Status Visualization . 87 6.3.1 Layout Algorithm . 87 6.3.2 Final Positions . 89 6.3.3 Confirmation . 89 6.3.4 Scale . 90 6.3.5 User Interaction . 90 6.3.6 Final Remarks . 91 6.4 Multi-Circular Visualization . 91 6.4.1 Macro-Level Layout . 93 6.4.2 Micro-Level Layout Algorithm . 93 6.4.3 Final Placement . 94 6.4.4 Final Remarks . 95 6.5 Additional Positional Visualizations . 95 6.5.1 Coordinate Visualization . 95 6.5.2 Group Visualization . 96 6.6 Examples . 97 6.6.1 The Network of the Deutschland AG . 97 6.6.2 Email Communication Network . 98 7 Layout Algorithms 101 7.1 Circular Crossing Reduction . 101 7.1.1 Introduction . 101 7.1.2 Preliminaries . 102 7.1.3 Initial Greedy Layout . 103 7.1.4 Improvement by Circular Sifting . 105 6 Contents 7.1.5 Constraint Crossing Reduction . 107 7.1.6 Experimental Evaluation . 109 7.1.7 Conclusion . 111 7.2 Multi-Circular Layout of Micro/Macro Graphs . 112 7.2.1 Preliminaries . 112 7.2.2 Macro Layout . 113 7.2.3 Related (Micro-) Layout . 114 7.2.4 Multi-Circular Layout . 115 7.2.5 Layout Algorithms . 118 7.2.6 Conclusion . 123 7.3 Visualizing Hierarchies in Two and a Half Dimensions . 123 7.3.1 Introduction . 124 7.3.2 Preliminaries . 124 7.3.3 Layout Method . 125 7.3.4 Results . 126 7.3.5 Conclusion . 129 8 Network Models 133 8.1 Fundamental Models . 133 8.1.1 General Random Graphs . 133 8.1.2 Small World . 135 8.1.3 Preferential Attachment . 136 8.2 k-Core Generation using PA . 137 8.2.1 Preliminaries . 139 8.2.2 Core Generator . 141 8.2.3 Modeling the AS Network . 147 8.2.4 Conclusion . 155 Bibliography 157 Index 177 Appendix 179 R´esum´e 189 Chapter 1 Zusammenfassung 1.1 Uberblick¨ Seit einigen Jahren werden wirtschaftliche und gesellschaftliche Entwicklungen im- mer h¨aufiger unter dem Aspekt der \Vernetzung" betrachtet. Fur¨ das Verst¨andnis von Ereignissen ist dabei nicht mehr die institutionelle Position des Einzelnen, son- dern die Verbindungen der Handelnden untereinander und das sich daraus erge- bende Netzwerk entscheidend. Außer in sozialen Prozessen treten Netzwerke auch in vielen weiteren Bereichen auf, beispielsweise als elektronische Schaltkreise, tech- nische Kommunikationsnetze oder als weltumspannende Transportnetzwerke. Ent- sprechend diesem breiten Anwendungsbereich sind die relevanten Fragestellungen sehr vielf¨altig und die betrachteten Netzwerke unterscheiden sich deutlich in Gr¨oße und Auspr¨agung. Bereiche der Informatik, die Methoden fur¨ die Netzwerkanalyse bereitstellen k¨onnen, sind offensichtlich die Graphentheorie, und da sich die Visua- lisierungen der Netzwerke anbietet, das Graphenzeichnen, aber auch viele andere Bereiche wie Algorithmik und Kombinatorik. Entsprechend der gestiegenen Relevanz wird auch geeignete Software zur Analyse und Visualisierung von Netzwerken wichtiger. In dieser Arbeit wird die Software visone fur¨ diese Aufgabe vorgestellt, die kostenlos von der Homepage [vpt] bezo- gen werden kann. Obwohl das Projekt ursprunglich¨ in Kooperation mit Sozialwis- senschaftlern gestartet wurde und deshalb den Begriff soziale Netzwerkanalyse im Namen fuhrt,¨ lag ein Schwerpunkt der Entwicklung immer auf der allgemeinen An- wendbarkeit. Da viele der verwendeten Modelle und Methoden universell sind, ist eine strikte Abgrenzung auch kaum m¨oglich und sinnvoll. Wichtige weitere Design- ziele sind • die Bereitstellung eines geeigneten universellen Dateiformats, • exakt definierte und allgemein anwendbare Analyseverfahren, • Netzwerkvisualisierungen, die sowohl die Analyseergebnisse exakt wiedergeben als auch die Netzwerkstruktur ubersichtlich¨ darstellen und • eine fur¨ nicht-technische Benutzer verst¨andliche Bedienung. 8 Chapter 1: Zusammenfassung visone erm¨oglicht durch die vollst¨andig integrierte graphische Anzeige- und Edi- torkomponente einen.
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