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

This article addresses visual exploration of 3D information layouts. Several visual exploration techniques have been proposed for 2D information layouts. Many of these try to take advantage of humans' natural visual pattern-recognition abilities to understand global relationships while simultaneously integrating this knowledge with local details. This desire for detail-incontext views (also called fisheye, multiscale, and distortion views) has fueled considerable research in the development of distortion viewing tools. Generally, these tools provide

Making effective use of the available display space has long been a fundamental issue in user interface design. We live in a time of rapid advances in available CPU power and memory. However, the common sizes of our computational display spaces have only minimally increased or in some cases, such as hand held devices, actually decreased. In addition, the size and scope of the information spaces we wish to explore are also expanding. Representing vast amounts of information on our relatively small screens has become increasingly problematic and has been associated with problems in navigation, interpretation and recognition. User interface research has proposed several differing presentation approaches to address these problems. These methods create displays that vary considerably, visually and algorithmically. We present a unified framework that provides a way of relating seemingly distinct methods, facilitating the inclusion of more than one presentation method in a single interface. Furthermore, it supports extrapolation between the presentation methods it describes. Of particular interest are the presentation possibilities that exist in the ranges between various distortion presentations, magnified insets and detail-in-context presentations, and between detail-incontext presentations and a full-zooming environment. This unified framework offers a geometric presentation library in which presentation variations are available independently of the mode of graphic representation. The intention is to promote the ease of exploration and experimentation into the use of varied presentation combinations.

... representation of nonlinear magnification, providing methods for converting transformation routines to magnification fields and vice-versa. This new representation provides ease of manipulation and power of expression. By removing the restrictions of explicit foci and allowing precise specification of magnification values, we can achieve magnification effects which were not previously possible. Of particular interest are techniques we introduce for expressing complex and subtle magnification effects through magnification brushing, and allowing intrinsic properties of the data being visualized to create data-driven magnifications.

This paper describes a general formulation of the "detail-in-context" problem, which is a central issue of fundamental importance to a wide variety of nonlinear magnification systems. A number of tools are described for dealing with this problem effectively. These tools can be applied to any continuous nonlinear magnification system, and are not tied to specific implementation features of the system that produced the original transformation. Of particular interest is the development of "seamless multi-level views", which allow multiple global views of an information space (each having different information content) to be integrated into a single view without discontinuity. 1.

An increasing number of tasks require people to explore, navigate and search extremely complex data sets visualized as graphs. Examples include electrical and telecommunication networks, web structures, and airline routes. The problem is that graphs of these real world data sets have many interconnected nodes, ultimately leading to edge congestion: the density of edges is so great that they obscure nodes, individual edges, and even the visual information beneath the graph. To address this problem we developed an interactive technique called EdgeLens. An EdgeLens interactively curves graph edges away from a person’s focus of attention without changing the node positions. This opens up sufficient space to disambiguate node and edge relationships and to see underlying information while still preserving node layout. Initially two methods of creating this interaction were developed and compared in a user study. The results of this study were used in the selection of a basic approach and the subsequent development of the EdgeLens. We then improved the EdgeLens through use of transparency and colour and by allowing multiple lenses to appear on the graph.

Figure 1: Magic volume lens results. (a) magnifying inside features in an arbitrary-shaped area on an engine, (b) applying sampling-rate-based lens on a foot, (c) enlarging area of interest on an aneurism, (d) magnifying the duodenum of a segmented frog dataset. The size and resolution of volume datasets in science and medicine are increasing at a rate much greater than the resolution of the screens used to view them. This limits the amount of data that can be viewed simultaneously, potentially leading to a loss of overall context of the data when the user views or zooms into a particular area of interest. We propose a focus+context framework that uses various standard and advanced magnification lens rendering techniques to magnify the features of interest, while compressing the remaining volume regions without clipping them away completely. Some of these lenses can be interactively configured by the user to specify the desired magnification patterns, while others are featureadaptive. All our lenses are accelerated on the GPU. They allow the user to interactively manage the available screen area, dedicating more area to the more resolution-important features.

. ACTIVEMAP is a visualization tool that enables users to gain greater awareness of the location of people in their workplace environment, increasing each person's ability to seek out colleagues for informal, face-to-face interactions. Our initial implementation of the tool places images of each person's face on a map of the building. We have explored variations on how to best represent a range of features: the "freshness" of location information, groups of people in a single office, and the movement of people throughout the environment. We describe the context of the environment in which the tool is used, the features embodied in this tool, variations we have implemented for representing location and movement information, and some potential extensions for future versions of the tool. 1. Introduction Informal interactions constitute a frequent and crucial aspect of accomplishing work [Isaacs, et al., 1993]. A number of other researchers have explored issues of awareness [Do...

The WWW has a great potential of evolving into aglobally distributed digital document library.The primary use of such a library is to retrieve information quickly and easily. Because of the size of these libraries, simple keyword searches often result in too many matches. More complex searches involving boolean expressions are di cult to formulate and understand. This paper describes QBT (Query By Templates), a visual method for formulating queries for structured document databases modeled with SGML. Based on Zloof's QBE (Query By Example), this method incorporates the structure of the documents for composing powerful queries. The goal of this technique is to design an interface for querying structured documents without prior knowledge of the internal structure. This paper describes the rationale behind QBT, illustrates the query formulation principles using QBT, and describes results obtained from a usability analysis on a prototype implementation of QBT on the Web using the Java TM programming language. 1

The difficulty of accessing information details while preserving context has generated many different focus-incontext techniques. A common limitation of focus-incontext techniques is their ability to work well at high magnification. We present a set of improvements that will make high magnification in context more feasible. We demonstrate new distortion functions that effectively integrate high magnification within its context. Finally, we show how lenses can be used on top of other lenses, effectively multiplying their magnification power in the same manner that a magnifying glass applied on top of another causes multiplicative magnification. The combined effect is to change feasible detail-in-context magnification factors from less than 8 to more than 40.