This is a survey on graph visualization and navigation techniques, as used in information visualization. Graphs appear in numerous applications such as web browsing, state--transition diagrams, and data structures. The ability to visualize and to navigate in these potentially large, abstract graphs is often a crucial part of an application. Information visualization has specific requirements, which means that this survey approaches the results of traditional graph drawing from a different perspective. Index Terms---Information visualization, graph visualization, graph drawing, navigation, focus+context, fish--eye, clustering. 1

Abstract — Social network analysis (SNA) has emerged as a powerful method for understanding the importance of relationships in networks. However, interactive exploration of networks is currently challenging because: (1) it is difficult to find patterns and comprehend the structure of networks with many nodes and links, and (2) current systems are often a medley of statistical methods and overwhelming visual output which leaves many analysts uncertain about how to explore in an orderly manner. This results in exploration that is largely opportunistic. Our contributions are techniques to help structural analysts understand social networks more effectively. We present SocialAction, a system that uses attribute ranking and coordinated views to help users systematically examine numerous SNA measures. Users can (1) flexibly iterate through visualizations of measures to gain an overview, filter nodes, and find outliers, (2) aggregate networks using link structure, find cohesive subgroups, and focus on communities of interest, and (3) untangle networks by viewing different link types separately, or find patterns across different link types using a matrix overview. For each operation, a stable node layout is maintained in the network visualization so users can make comparisons. SocialAction offers analysts a strategy beyond opportunism, as it provides systematic, yet flexible, techniques for exploring social networks. Index Terms—Social networks, interactive graph visualization, attribute ranking, coordinated views, exploratory data analysis. 1

We present a discussion and initial empirical investigation of user interface designs for a set of three Web browsers. The user study demonstrated the strengths and weaknesses of two conventional 2D browsers, as well as that of XML3D, a novel browser that integrates an interactive 3D hyperbolic graph view with a more traditional 2D list view of the data. A standard collapse/expand tree browser and a Web-based hierarchical categorization similar to Yahoo!, were competitively evaluated against XML3D. No reliable difference between the two 2D browsers was observed. However, the results showed clear differences between XML3D and the 2D user interfaces combined. With XML3D, participants performed search tasks within existing categories reliably faster with no decline in the quality of their responses. It was informally observed that integrating the ability to view the overall structure of the information space with the ability to easily assess local and global relationships was key to successful search performance. XML3D was the only tool of the three that efficiently showed the overall structure within one visualization. The XML3D browser accomplished this by combining a 3D graph layout view as well as an accompanying 2D list view. Users did opt to use the 2D user interface components of XML3D during new category search tasks, and the XML3D performance advantage was no longer obtained in those conditions. In addition, there were no reliable differences in overall user satisfaction across the three user interface designs. Since we observed subjects using the XML3D features differently depending on the kind of search task, future studies should explore optimal ways of integrating the use of novel focus + context visualizations and 2D lists for effective information retrieval. The contribution of this paper is that it includes empirical data to demonstrate where novel focus + context views might benefit users over and above more conventional user interface techniques, in addition to where design improvements are warranted.

This paper proposes a new visualization and interaction technique for medium-sized trees, called Collapsible Cylindrical Trees (CCT). Child nodes are mapped on rotating cylinders, which will be dynamically displayed or hidden to achieve a useful balance of detail and context. Besides a comprehensible three-dimensional visualization of trees, the main feature of CCT is a very fast and intuitive interaction with the displayed nodes. Just one click is needed to reach every node and perform an action on it such as displaying a web page. The CCT browsing technique was developed for interaction with web hierarchies but is not limited to this domain. We also present sample implementations of CCT using VRML, which show the usefulness of this intuitive tree navigation technique.

We describe a new animation technique for supporting interactive exploration of a graph, building on the wellknown radial tree layout method. When a node is selected to become the center of interest, our visualization performs an animated transition to a new layout. Our approach is to linearly interpolate the polar coordinates of the nodes, while enforcing constraints on the layout to keep the transition easy to follow. We apply this technique to visualizations of social networks and of the Gnutella file-sharing network, and discuss our findings and usability results. Key Words: graph drawing, animation, interaction 1.

knowledge representation and information management by building a structured semantic network above information resources. Our research at LIP6 aims at visualizing this semantic layer efficiently, which is a critical issue as Topic Maps may contain millions of elements.

It has been known for some time that larger graphs can be interpreted if laid out in 3D and displayed with stereo and/or motion depth cues to support spatial perception. However, prior studies were carried out using displays that provided a level of detail far short of what the human visual system is capable of resolving. Therefore we undertook a graph comprehension study using a very high resolution stereoscopic display. In our first experiment we examined the effect of stereo, kinetic depth and using 3D tubes versus lines to display the links. The results showed a much greater benefit for 3D viewing than previous studies. For example, with both motion and depth cues, unskilled observers could see paths between nodes in 333 node graphs with less than a 10 % error rate. Skilled observers could see up to a 1000 node graph with less than a 10 % error rate. This represented an order of magnitude increase over 2D display. In our second experiment we varied both nodes and links to understand the constraints on the number of links and the size of graph that can be reliably traced. We found the difference between number of links and number of nodes to best account for error rates and suggest that this is evidence for a “perceptual phase transition”. These findings are discussed in terms of their implications for information display.

Abstract—Online pick’em games, such as the recent NCAA college basketball March Madness tournament, form a large and rapidly growing industry. In these games, players make predictions on a tournament bracket that defines which competitors play each other and how they proceed toward a single champion. Throughout the course of the tournament, players monitor the brackets to track progress and to compare predictions made by multiple players. This is often a complex sensemaking task. The classic bracket visualization was designed for use on paper and utilizes an incrementally additive system in which the winner of each match-up is rewritten in the next round as the tournament progresses. Unfortunately, this representation requires a significant amount of space and makes it relatively difficult to get a quick overview of the tournament state since competitors take arbitrary paths through the static bracket. In this paper, we present AdaptiviTree, a novel visualization that adaptively deforms the representation of the tree and uses its shape to convey outcome information. AdaptiviTree not only provides a more compact and understandable representation, but also allows overlays that display predictions as well as other statistics. We describe results from a lab study we conducted to explore the efficacy of AdaptiviTree, as well as from a deployment of the system in a recent real-world sports tournament. Index Terms—Online fantasy sports, tournament, bracket, picks, adaptive tree visualization. 1

In this paper we present a topology viewer for the NaradaBrokering [FP02] system. The NaradaBrokering system comprises a distributed network of cooperating broker nodes organized within a logical overlay network. The topology viewer’s layout algorithm is implemented such that it augments the structure of the NaradaBrokering network. Furthermore, we believe that this approach could also be applied to similar visualization problems. Our visualization scheme extends recent work in the visualization of large hierarchies with primary focus on algorithmic and visual simplicity. Specifically, we have modified the ringed layout algorithm for placement of various NaradaBrokering components in order to achieve navigational efficiency. The scheme also helps user view information associated with nodes and links besides navigating through the network hierarchy. We have tested the topology viewer with up to ten thousand nodes and we include these performance measurements in this paper. Visualization of network topologies is a challenging problem. Networks can be thought of as graphs. A graph has two main components – a set of nodes and a set of edges (relations). Given a set of nodes and a corresponding set of edges, the basic graph drawing problem involves the calculation of the position of the nodes and the curve that needs to be drawn for each edge [HMM00]. There are number of factors which decide the quality

We describe a new animation technique for supporting interactive exploration of a graph. We use the wellknown radial tree layout method, in which the view is determined by the selection of a focus node. Our main contribution is a method for animating the transition to a new layout when a new focus node is selected. In order to keep the transition easy to follow, the animation linearly interpolates the polar coordinates of the nodes, while enforcing ordering and orientation constraints. We apply this technique to visualizations of social networks and of the Gnutella file-sharing network, and discuss the results from our informal usability tests.