Extraction and Analysis of Facebook Friendship Relations

Online Social Networks (OSNs) are a unique Web and social phenomenon, affecting tastes and behaviors of their users and helping them to maintain/create friendships. It is interesting to analyze the growth and evolution of Online Social Networks both from the point of view of marketing and other of new services and from a scientific viewpoint, since their structure and evolution may share similarities with real-life social networks. In social sciences, several techniques for analyzing (online) social networks have been developed, to evaluate quantitative properties (e.g., defining metrics and measures of structural characteristics of the networks) or qualitative aspects (e.g., studying the attachment model for the network evolution, the binary trust relationships, and the link prediction problem).\ud However, OSN analysis poses novel challenges both to Computer and Social scientists. We present our long-term research effort in analyzing Facebook, the largest and arguably most successful OSN today: it gathers more than 500 million users. Access to data about Facebook users and their friendship relations, is restricted; thus, we acquired the necessary information directly from the front-end of the Web site, in order to reconstruct a sub-graph representing anonymous interconnections among a significant subset of users. We describe our ad-hoc, privacy-compliant crawler for Facebook data extraction. To minimize bias, we adopt two different graph mining techniques: breadth-first search (BFS) and rejection sampling. To analyze the structural properties of samples consisting of millions of nodes, we developed a specific tool for analyzing quantitative and qualitative properties of social networks, adopting and improving existing Social Network Analysis (SNA) techniques and algorithms

Minimum-width graph layering revisited

The minimum-width layering problem tackles one step of a layout pipeline to create top-down drawings of directed acyclic graphs. Thereby, it aims at keeping the overall width of the drawing small. We study layering heuristics for this problem as presented by Nikolov et al. as well as traditional layering methods with respect to the questions how close they are to the true minimal width and how well they perform in practice, especially, if a particular drawing area is prescribed. We find that when applied carefully and at the right moment the layering heuristics can, compared to traditional layering methods, produce better layerings for prescribed drawing areas and for graphs with varying node dimensions. Still, we also find that there is room for improvement

RELT - Visualizing trees on mobile devices

The small screens on increasingly used mobile devices challenge the traditional visualization methods designed for desktops. This paper presents a method called "Radial Edgeless Tree" (RELT) for visualizing trees in a 2-dimensional space. It combines the existing connection tree drawing with the space-filling approach to achieve the efficient display of trees in a small geometrical area, such as the screen that are commonly used in mobile devices. We recursively calculate a set of non-overlapped polygonal nodes that are adjacent in the hierarchical manner. Thus, the display space is fully used for displaying nodes, while the hierarchical relationships among the nodes are presented by the adjacency (or boundary-sharing) of the nodes. It is different from the other traditional connection approaches that use a node-link diagram to present the parent-child relationships which waste the display space. The hierarchy spreads from north-west to south-east in a top-down manner which naturally follows the traditional way of human perception of hierarchies. We discuss the characteristics, advantages and limitations of this new technique and suggestions for future research. © Springer-Verlag Berlin Heidelberg 2007

Visual Debugging of Object-Oriented Systems with the Unified Modeling Language

The Department of Defense (DoD) is developing a Joint Battlespace Infosphere, linking a large number of data sources and user applications. Debugging and analysis tools are required to aid in this process. Debugging of large object-oriented systems is a difficult cognitive process that requires understanding of both the overall and detailed behavior of the application. In addition, many such applications linked through a distributed system add to this complexity. Standard debuggers do not utilize visualization techniques, focusing mainly on information extracted directly from the source code. To overcome this deficiency, this research designs and implements a methodology that enables developers to analyze, troubleshoot and evaluate object-oriented systems using visualization techniques. It uses the standard UML class diagram coupled with visualization features such as focus+context, animation, graph layout, color encoding and filtering techniques to organize and present information in a manner that facilitates greater program and system comprehension. Multiple levels of abstraction, from low-level details such as source code and variable information to high-level structural detail in the form of a UML class diagram are accessible along with views of the program s control flow. The methods applied provide a considerable improvement (up to 1110%) in the number of classes that can be displayed in a set display area while still preserving user context and the semantics of UML, thus maintaining system understanding. Usability tests validated the application in terms of three criteria software visualization, debugging, and general system usability