The VCG tool allows the visualization of graphs that occur typically as data structures in programs. We describe the functionality of the VCG tool, its layout algorithm and its heuristics. Our main emphasis in the selection of methods is to achieve a very good performance for the layout of large graphs. The tool supports the partitioning of edges and nodes into edge classes and nested subgraphs, the folding of regions, and the management of priorities of edges. The algorithm produces good drawings and runs reasonably fast even on very large graphs.

We present the graph visualization system daVinci, an interactive tool that can be used by arbitrary application programs as a user interface for graph data structures. Beside a novel automatic layout algorithm for graphs, daVinci offers many interactive facilities such as fine-tuning of a layout, abstractions and scaling operations. A bidirectional application interface is used for tool communication with a program that controls the graph structure.

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Users often must browse hierarchies with thousands of nodes in search of those that best match their information needs. The PDQ Tree-browser (Pruning with Dynamic Queries) visualization tool was specified, designed and developed for this purpose. This tool presents trees in two tightlycoupled views, one a detailed view and the other an overview. Users can use dynamic queries, a method for rapidly filtering data, to filter nodes at each level of the tree. The dynamic query panels are user-customizable. Subtrees of unselected nodes are pruned out, leading to compact views of relevant nodes. Usability testing of the PDQ Tree-browser, done with 8 subjects, helped assess strengths and identify possible improvements. The PDQ Tree-browser was used in Network Management (600 nodes) and UniversityFinder (1100 nodes) applications. A controlled experiment, with 24 subjects, showed that pruning significantly improved performance speed and subjective user satisfaction. Future research directions ar...

. Grasper-CL is a system for manipulating and displaying graphs, and for building graph-based user interfaces for application programs. It is implemented in COMMON LISP and CLIM, and has been proven by use in a number of applications. Grasper-CL includes several advances in graph drawing. It contains a graph abstract datatype plus a comprehensive and novel language of operations on that datatype. The appearance of Grasper-CL graphs can be tailored by a wide variety of shape parameters that allow the application to customize the display of nodes and edges for different domains. Default values for shape parameters can be established at several levels. Grasper-CL employs a toolbox approach to graph layout: the system contains a suite of graph layout algorithms that can be applied individually, or in combination to produce hierarchical graph layouts. The system also contains an interactive graph browser. Keywords: Graphs, Graph drawing, Graph layout 1. Introduction Graphs are virtually ubi...

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Dynamic Fisheye Views: Combining Dynamic Queries and Mapping with Database View Definition Doctor of Philosophy, 1996 Department of Computer Science University of Toronto Information (or data) visualization refers to the graphical presentation of information with the aim of providing the viewer with a qualitative understanding of the information contents. Two common graphical methods for depicting multidimensional data are scatterplots (that show relationships among data dimensions) and node-andlink diagrams or graphs (that show relationships among individual data points). One strategy to aid understanding of multidimensional data is to map data dimensions or attributes (e.g., temperature, population, location) to graphic properties (e.g., colour, size, position). Dynamic mapping (DM) is an interactive technique that permits mappings to be adjusted dynamically. The dynamic query (DQ) is a related interactive technique that applies the principles of direct manipulation to the sea...

We present a method for the layout of compound directed graphs that is based on the hierarchical layer layout method. Our method has similarities with the method of Sugiyama and Misue [7] but gives different results: It uses a global partitioning into layers and tries to produce placements of nodes such that border rectangles can be drawn around the nodes of each subgraph. The method is implemented in the VCG tool.

A constraint is a relation that we would like to maintain. Over the last thirty years, a number of problems have prevented constraints from being widely accepted for use in interactive graphical applications. The biggest difficulty of applying constraints has been finding the right tradeoff between performance and expressiveness. To be able to satisfy systems of constraints efficiently enough for real-time use, interactive applications have restricted the problem to solving less-expressive sets of constraints. One common such restriction is to require that the constraint relationships are acyclic, thus enabling simple techniques based on local propagation. Unfortunately, these limitations in expressiveness counteract the benefits that the declarative specification of relationships with constraints is inten...

Constraints provide a declarative means for specifying relationships that we wish to hold true. Interactive graphical applications give rise to varying kinds of constraints, and researchers have developed diverse constraint solving techniques. I survey the classes of constraints used by numerous drawing, graph layout, visualization and animation systems. I describe a taxonomy of the constraint solving methods used to satisfy these systems and compare solver expressiveness and performance. Though backtracking algorithms have not yet been used successfully in interactive graphical applications, I summarize work on various backtracking algorithms and suggest ways to begin to improve their performance so they might be used in the user interface domain. 1 Introduction From the inception of graphical user interfaces, systems have tried to use constraints to maintain relationships among on-screen entities [Sut63]. Constraints permit the designers or users of a system to express what they wis...