Kenneth C. Cox

A taxonomy of program visualization systems

A taxonomy of program visualization systems that is based on a model of program visualization that maps programs to graphical representations is presented. The taxonomy is illustrated with three program visualization systems representative of research trends: Zeus, Tango, and Pavane.<<ETX>>

Pavane : A System for Declarative Visualization of Concurrent Computations

Abstract This paper describes the conceptual model, specification method and visualization methodology for Pavane —a visualization environment concerned with exploring, monitoring and presenting concurrent computations. The underlying visualization model is declarative in the sense that visualization is treated as a mapping from program states to a three-dimensional world of geometric objects. The latter is rendered in full color and may be examined freely by a viewer who is allowed to navigate through the geometric world. The state-to-geometry mapping is defined as a composition of several simpler mappings. The choice is determined by methodological and architectural considerations. This paper shows how this decomposition was molded by two methodological objectives: (1) the desire visually to capture abstract formal properties of programs (e.g. safety and progress) rather than operational details; and (2) the need to support complex animations of atomic computational events. All mappings are specified using a rule-based notation; rules may be added, deleted and modified at any time during the visualization. An algorithm for termination detection in diffusing computations is used to illustrate the specification method and to demonstrate its conceptual elegance and flexibility. A concurrent version of a popular artificial intelligence program provides a vehicle for demonstrating how we derive graphical representations and animation scenarios from key formal properties of the program, i.e. from those safety and progress assertions about the program which turn out to be important in verifying its correctness.

A declarative approach to visualizing concurrent computations

The authors explore the graphical representation of objects and processes as a means for understanding programs consisting of large numbers of concurrent processes. Their goal is to establish a technical foundation for research into the monitoring and debugging of large-scale concurrent programs. They explain declarative visualization and introduce some shared-data-space concepts and notation by means of a simple, nondeterministic, parallel algorithm. They discuss visual abstraction and their visualization methodology, which they illustrate by applying it to region labeling. Thy examine the relaxation of nonintervention that visualization makes possible.<<ETX>>

Program visualization: the art of mapping programs to pictures

In this paper program visualization is defined as a mapping from programs to graphical representations. Simple forms of program visualization are frequently encountered in software engineering. For this reason current advances in program visualization are likely to influence future developments concerning software engineering tools and environments. This paper provides a new taxonomy of program visualization research. The proposed taxonomy becomes the vehicle through which we carry out a systernatic review of current systems, techniques, trends, and ideas in program visualization.

Abstraction in algorithm animation

Abstraction of information into visual form plays a key role in the development of algorithm animations. The authors present a classification for abstraction as applied to algorithm animation. The classification emphasizes the expressive power of the abstraction ranging from simple direct presentation of the programs state to complex animations intended to explain the behavior of the program. They illustrate their classification by presenting several visualizations of a shortest path algorithm.<<ETX>>

Visualizing concurrent computations

The paper describes the conceptual model and specification method for a visualization environment concerned with exploring, monitoring, and presenting concurrent computations. The model is declarative in that visualization is treated as a mapping from program states to a three-dimensional geometric world. The state-to-geometry mapping is defined as a composition of several simpler mappings. This paper shows how this decomposition was molded by two methodological objectives: (1) the desire to visually capture abstract formal properties of programs and (2) the need to support complex animations of atomic computational events. A termination detection algorithm is used to illustrate the specification method and to demonstrate its conceptual elegance and flexibility.<<ETX>>

Declarative Visualization In The Shared Dataspace Paradigm

This paper is concerned with the use of program visualization as a means for the understanding, debugging, and monitoring of large-scale concurrent programs. Following an overview of the shared dataspace paradigm and the declarative approach to visualization, the paper discusses: (1) mechanisms for specifying declarative visualization in the shared dataspace paradigm and ways of relating the specifications to program verification; (2) a computational model which provides a unified framework for comparing both visual and nonvisual algorithms; and (3) strategies for implementing declarative visualization on parallel machines.

A Characterization of the Computational Power of Rule-based Visualization

Abstract Declarative visualization is a paradigm in which the process of visualization is treated as a mapping from some domain (typically a program) to an image. One means of declaring such mappings is through the use of rules which specify the relationship between the domain and the image. This paper examines the computational power of such rule-based mappings, focusing on their ability to construct the types of images typically desired in program visualization applications.

Interactive complexity control and high-speed stereo matching

The authors are concerned with the development of a novel approach to edge-based stereo matching. In the context of an incremental matching strategy the authors have replaced the traditional hierarchical (coarse-fine) matching by an approach called complexity control based matching. The implementation of this method allows the user to select interactively features which (given the context provided by previous matches) are most likely to be matched successfully. The selection is done at the resolution of the original image and utilizes a rich set of feature properties (e.g. edge strength, orientation, length, texture etc.), either alone or in logical combinations. Both feature-selection and feature-matching algorithms execute at real-time rates, and all interactions are via a stereo workstation.<<ETX>>

Rapid search for spherical objects in aerial photographs

A methodology is presented for designing detectors which locate specific features in an image. The method is applied to the detection and segmentation of spherical features. A vital part of the detection and segmentation is the use of the gradient angle transform. An analysis of the gradient angle for ideal spheres is presented, with a discussion of how this may be used to locate the boundaries of the sphere. The algorithms used by a program which detects and segments spherical features are then presented. The results of applying the program to images with man-made spherical features are given.<<ETX>>