. 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...

What are the hottest computer science research topics today? Which research areas are experiencing steady decline? How many co-authors are typical for a research paper today and 20 years ago? Who are the most prolific writers? In this paper, we attempt to address these questions as well as study collaboration patterns, research communities, interactions between related research specialties, and the evolution of these characteristics through time. For our analysis we use data from the Association of Computing Machinery's Digital Library of Scientific Literature (ACM Portal) which contains over a hundred thousand research papers and authors. We use a novel technique for visualization of large graphs that evolve through time. Given a dynamic graph, the layout algorithm produces two-dimensional representations of each time-slice, while preserving the mental map of the graph from one slice to the next. A combined view, with all the time-slices can also be viewed and explored. Graphs with tens of thousands of vertices and edges, resulting from specific queries to our local copy of the ACM database, are generated and displayed in seconds. The images in this paper are produced by a graph layout tool which uses the dynamic graph layout algorithm.

Every interactive system requires a presentation mechanism, to show the user the data it handles. Often, the relationship between the data and its presentation is complex; further, it is often mediated by astyle mechanism, allowing the user or a designer to describe how the data should be displayed. It is a standing engineering challenge to develop a presentation model that is exible, handling many kinds of data and layout; powerful, giving the user extensive control over appearance; and e cient enough for interactive work. In this dissertation, we propose a model of presentation by tree transformation. Because information often has a hierarchical logical structure, trees are widely used to represent documents and other data. The layout or presentation of a document is also often modeled as a computation over a tree. But these trees are not generally identical. In other words, presentation can be seen as a mapping between trees. Casting it as a formal tree transformation o ers both expressive, compact style speci cations and e cient implementation. We present a general framework for presentation by tree transformation. It has been implemented as part of Ensemble, a software development environment and multimedia document system

Among existing tools for laying out large collections of visual objects, some perform automatic layouts, possibly following some rules prespecified by the user, e.g., graph layout tools, while others let users specify layouts manually, e.g., CAD design tools. Most of them canonly deal with specific types of visualizations, e.g., graphs, and some of them allow users to view visual objects at various levels of detail, e.g., tree-structure visualization tools. In this paper, we develop techniques that strike a balance between user specification and automatic generation of layouts, work at multiple granularities, and are generally applicable. In particular, we introduce a general framework and layout algorithm that (a) deals with arbitrary types of visual objects, (b) allows objects to be viewed in any one of several different visual representations (at different levels of detail) , and (c) uses a small number of user-specified layouts to guide heuristic decisions for automatically derivin...

In software visualization and algorithm animation it is important that advances in system technologies are accompanied by corresponding advances in animation presentations. In this paper we describe methods for animating tree manipulation algorithms, one of the most challenging algorithm animation domains. In particular, we animate operations on pairing heap data structures which are used to implement priority queues. Our animations use tree layout heuristics and and smooth transitions for illustrating intermediate algorithm states to promote viewer understanding. This paper describes the visual techniques and methodologies used to display the pairing heap operations. The paper also details the implementation requirements and how our particular support platform, the XTango system, facilitates meeting these requirements. 1 Introduction Algorithm animations[Bro88b] visually depict how algorithms function to promote understanding of the algorithm's methodologies. Usually, the animation...

Many activities in computer graphics can be regarded as experiments on virtual objects or models. In the process of experimentation the existing models are gradually improved and new model categories emerge. The Virtual Laboratory (vlab) is a software environment designed to support model development by facilitating the manipulation of models and providing mechanisms for storing and retrieving large numbers (e.g., thousands) of them. The models can be shared between users who work at different geographical locations over the Internet. In the paper we first clarify the essential concept of the Virtual Laboratory by describing its operation from a user's perspective. The modeling of plants serves as a sample application. We then present the key elements of vlab design and implementation, discuss the obtained results, and present their possible ramifications in the context of related ideas.

A new X-Windows object -- Graph widget -- will be presented. It handles graphs using one of the three graph layout functions implemented: trees, hierarchical graphs and general graphs. The widget interface to Prolog allowing its utilization in logical programming environments and some of the possible widget applications will also be described.

We study the problem of designing layout facilities for the navigation of an "infinite" graph, i.e. a graph that is so large that its visualization is unfeasible, even by gluing together all the screen snapshots that a user can take during the navigation. We propose a framework for designing layout facilities that support the navigation of an infinite tree. The framework allows to exploit the knowledge of future moves of the user in order to reduce the changes in her mental map during the navigation. Variants of the classical Reingold-Tilford algorithm are presented and their performance is studied both experimentally and analytically. 1 Introduction Designing layout facilities for the navigation of "infinite" graphs is one of the challenges of the Graph Drawing field. By "infinite" we mean that it would be unfeasible to visualize the graph entirely, even by gluing together all the screen snapshots that a user can take during the navigation. Examples of graphs that can be considered i...

This article summarises the current state of research into multiple tree visualisations. It discusses the spectrum of current representation techniques used on single trees, pairs of trees and finally multiple trees, in order to identify which representations are best suited to particular tasks and to find gaps in the representation space, in which opportunities for future multiple tree visualisation research may exist. The application areas from where multiple tree data are derived are enumerated, and the distinct structures that multiple trees make in combination with each other and the effect on subsequent approaches to their visualisation are discussed, along with the basic high-level goals of existing multiple tree visualisations.

Graphs are widely and effectively used abstractions for organizing and visualizing information. In this paper we present a graph data structure for representing trees and a drawing framework for positioning the nodes such that the result is a planar radial layout. Radial drawings make good use of the screen space. An XML-based file format for the storing of graph data is presented. The design of the file format achieves data abstraction amongst its layers separating the data and the application. We use an object-oriented algorithmic paradigm. Classes with low cohesion that emphasize scalability and efficiency are produced. A prototype application is presented to test and exhibit the design. The framework and data structures are used to create a radial drawing application for a web-based course storyboard. The radial drawing is a graphical representation of the structure of the web-based course that can be used in the design of the course as well as used as the actual site map. In the prototype, the node structure is not the traditional point used by most graph-drawing applications but rather a complex structure with its own internal structure. A novel specialized design layout for these node structures in which the readability of text-based labels is maximized is offered. This adds to the data abstraction of the design, facilitating the reuse of layout information and improving the overall efficiency. The algorithms are linear with O (n) complexity. Through navigation of the site and interaction with the drawing, the user can alter the focus of the graph as required. This recentering of the graph incorporates animation features for dynamic graph drawing. 1.