Abstract not found

Empirical studies comparing the effectiveness of visual languages versus textual languages have rarely been attempted. Here we describe an experiment conducted on programmers solving vector and matrix manipulation tasks using the visual language Forms/3, the textual language Pascal, and a textual matrix manipulation language with the capabilities of APL. Presented here are our motivation, experimental approach, some of the difficulties experienced in attempting this type of empirical study, and a summary of the experimental results and insights gained.

We believe concreteness, direct manipulation and responsiveness in a visual programming language increase its usefulness. However, these characteristics present a challenge in generalizing programs for reuse, especially when concrete examples are used as one way of achieving concreteness. In this paper, we present a technique to solve this problem by deriving generality automatically through the analysis of logical relationships among concrete program entities from the perspective of a particular computational goal. Use of this technique allows a fully general form-based program with reusable abstractions to be derived from one that was specified in terms of concrete examples and direct manipulation.

In this paper, the uses of types and type inference in visual languages are explored. First, we discuss how the goals of a type system must differ for visual languages from those of a type system for textual languages. We then present a type system developed under these goals for the visual language Forms/3. Within the context of this system, issues of particular importance in visual languages are examined, including maintaining the user's conceptual model, the avoidance of language restrictions solely to support a type system, and how the visual process of programming can provide additional information to the type system. 1: Introduction One approach to types in visual programming languages (VPLs) is to hide them. The rationale would be to keep the simple, flexible spirit of programming in a visual language. This philosophy appears to be shared by many researchers, because few have introduced the concept of types into visual languages. But it seems contradictory to allow the user to u...

In this paper, we address the question of event-handling for declarative visual languages. In the approach presented, system-level, interactive, and user-defined events are fully-supported, while still maintaining the property of referential transparency. An approach to time termed temporal assignment provides a unifying mechanism for events to be defined as ordinary sequences of values, and conversely for ordinary sequences of values to be defined as events. This allows event-handling without additional concepts, and in particular provides a natural means for the user to define higher-level events of any kind. 1. Introduction Declarative programming languages effectively utilize visual programming techniques because declarative programming languages focus on the relationships between data as opposed to control flow, and these relationships tend to be inherently multi-dimensional. Yet, declarative programming languages have weaknesses in other areas which limit their usefulness for v...

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.

In this paper, we analyze performance characteristics of four prior one-way constraint maintenance implementation techniques, emphasizing how these characteristics influence responsiveness, and introduce a lazy optimization technique called culprit tracking. While culprit tracking is not a panacea in terms of raw speed, its performance characteristics significantly improve the consistency of responsiveness of GUIs maintained under the one-way constraint evaluation model. KEYWORDS: One-Way Constraints, Graphical User Interface Implementation Techniques 1. INTRODUCTION Programming graphical user interfaces by specifying the one-way constraints under which the dynamic, graphical objects should behave is an approach that has been used to support a wide range of user interface tasks. However, maintaining the constraints can be slow, especially if the system spends time processing variables that are not even necessary for keeping the screen up-to-date. In analyzing the properties of prior...