Objects + Scripts = Applications 1

We argue that object-oriented programming is only half of the story. Flexible, configurable applications can be viewed as collections of reusable objects conforming to standard interfaces together with scripts that bind these objects together to perform certain tasks. Scripting encourages a component-oriented approach to application development in which frameworks of reusable components (objects and scripts) are carefully engineered in an evolutionary software life-cycle, with the ultimate goal of supporting application construction largely from these interchangeable, prefabricated components. The activity of constructing the running application is supported by a visual scripting tool that replaces the textual paradigm of programming with a visual paradigm of direct manipulation and editing of both application and user interface components. We present scripting by means of some simple examples, and we describe a prototype of a visual scripting tool, called Vista. We conclude with some observations on the environmental support needed to support a component-oriented software life-cycle, using as a specific example the application development environment of ITHACA, a large European project of which Vista is a part.