In this paper we propose a new model, called Mocha, for providing algorithm animation over the World Wide Web. Mocha is a distributed model with a client-server architecture that optimally partitions the software components of a typical algorithm animation system, and leverages the power of the Java language, an emerging standard for distributing interactive platform-independent applications across the Web. Mocha provides high levels of security, protects the algorithm code, places a light communication load on the Internet, and allows users with limited computing resources to access animations of computationally expensive algorithms. The user interface combines fast responsiveness and user friendliness with the powerful authoring capabilities of hypertext narratives. We describe the architecture of Mocha and show its advantages over previous methods for algorithm animation over the Internet. We also present a prototype of an animation system for geometric algorithms that can be access...

Until now, only users of textual programming languages have enjoyed the fruits of algorithm animation. Users of visual programming languages (VPLs) have been deprived of the unique semantic insights algorithm animation offers, insights that would foster the understanding and debugging of visual programs. To begin solving this shortcoming, we have seamlessly integrated algorithm animation capabilities into Forms/3, a declarative VPL in which evaluation is the continuous maintenance of a network of one-way constraints. Our results show that a VPL that uses this constraint-based evaluation model can provide features not found in other algorithm animation systems. 1: Introduction Algorithm animation is a type of software visualization of growing importance. It is a dynamic visualization of the main abstractions of a program's underlying algorithm. The value of algorithm animation lies in its ability to portray the essence of the program's logic, avoiding the obscuring of this essence tha...

Animation is useful in user interfaces, especially for representing dynamic features. However, it is often difficult and laborious to create animation in an existing user interface environment. In this research, we extend our bi-directional translation model to deal with animations. The new model incorporates the notion of time, and includes operations defined for each representation in the model. Using this model, animation is basically achieved by interpolating successive visualized pictures of application data. Other than specifying the way of visualizing application data, programmers have only to provide mapping rules between abstract operations and interpolating methods, and as a result, complex animation effects can be easily specified. We have developed a prototype system based on this model, and applied it to several algorithm animations, such as sorting algorithms, the tower of Hanoi, and Kruskal’s algorithm. 1

Although the idea of reusing code is very appealing, effective reuse has long been acknowledged as a problem. To help address the difficulties, many advocate strong management commitment to code reuse, leading to the treatment of code as an asset to be carefully managed in a well-organized repository. However, the advent of the Web may bring a change to this outlook, encouraging informal, loosely-organized code repositories. Already, for both textual and visual languages, informal repositories are beginning to emerge, featuring a high rate of change and few controls over what a producer must do to submit code. In this paper, we present techniques to address some aspects of code reuse in this kind of informal, evolving environment. These techniques build upon characteristics found in many visual programming languages. Using these techniques, our approach is able to eliminate the special work traditionally required of the producer, while still supporting the consumer's reuse efforts with...

How might capabilities for algorithm animation be seamlessly integrated into a programming language that is both visual and declarative? Until now, visual programming language researchers have not attempted to anwer that question, making the fruits of algorithm animation available only to users of textual programming languages. Users of visual programming languages (VPLs) have been deprived of the unique semantic insights algorithm animation offers, insights that would foster the understanding and debugging of visual programs.

The visual nature of geometry applications makes it a natural area where visualization can be an effective tool for demonstrating algorithms. In this paper we propose a new model, called Mocha, for interactive visualization of algorithms over the World Wide Web. Mocha is a distributed model with a client-server architecture that optimally partitions the software components of a typical algorithm execution and visualization system, and leverages the power of the Java language, which has become the standard for distributing interactive platform-independent applications across the Web. Mocha provides high levels of security, protects the algorithm code, places a light communication load on the Internet, and allows users with limited computing resources to access executions of computationally expensive algorithms. The user interface combines fast responsiveness with the powerful authoring capabilities of hypertext narratives. We describe the architecture of Mocha, show its advan...

We describe an approach for visually teaching important proofs in the Junior-Senior level course on the design and analysis of data structures and algorithms (CS7/DS&A). The main idea of this educational paradigm is to justify important claims about data structures and algorithms by using pictures that visualize proofs so clearly that the pictures can qualify as proofs themselves. The advantage of using this approach for DS&A is that it augments or even replaces inductive arguments that many students find difficult. Moreover, this paradigm communicates important algorithmic facts in a compelling way for students who are more visually-oriented. We illustrate this technique by giving examples of visual proofs of several key concepts in DS&A. 1 Introduction In this era of real-time video games and MTV, students these days seem more visually-oriented than ever. They learn most naturally by seeing a concept described with a picture, and they remember that concept by recalling the picture ...

Early phases in the design of concurrent computer--based systems are known as critical and error-prone. Mistakes and wrong decisions during these phases can result in major breakdowns later on. Breakdowns usually require cost--intensive redesign or can lead to a failure of an entire project. A major problem in large designs is the comprehension of the individual componentinteraction. Visual languages can support designers with a better understanding of a system's behavior since they take advantage of people's visual system.

This thesis describes a framework for developing kinds of non-WIMP-based user interface software, designated as a bi-directional translation model. Here, ‘non-WIMP-based’ interface means that it cannot built only by combining WIMP widgets, such as buttons and menus. In particular, the targets of this thesis are two types of GUI software. One is direct manipulation interfaces for figures and diagrams that visually represent various abstract objects and relations in an application data, such as direct manipulation interfaces for network and hierarchical data structures. They enable the user to draw and modify diagrams to input abstract data into an application. Another is animations of changing abstract objects and relations in an application data, such as animations of sorting algorithms. They show their transitions visually, and are useful for understanding the behavior of an application or an algorithm. The bi-directional translation model models the general process of visualization, picture recognition, and animation generation. It is originated in Kamada’s general framework for visualizing abstract objects and relations. We have extended it by integrating recognition of figures/diagrams and animation of changing abstract objects and relations, which is one of the contributions in this thesis. The key idea of the framework is that these functions are translations between different data

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 systematic review of current systems, techniques, trends, and ideas in program visualization.