Alma: a Generic Program Animation System

In this paper, a system for program animation is presented. Alma system receives as input a computer program and produces a sequence of visualizations that will describe its functionality. The system generates automatically program animations basing this process on the internal representation of those programs. We do not rely upon any source program annotations (visual/animation statements, or parameters), neither on any special visual data types. The back-end of this system works over an execution tree (DAST), implementing the animation algorithm. This algorithm uses two bases of rules: visualizing rules (to associate graphical representation with program elements creating a visual description of the program state) and rewriting rules (to change the program state). We describe, in this paper, the Alma architecture and discuss the main algorithms that define the front-end and back-end. We also discuss the extensibility of the system in the sense of adding or modifying inputs and outputs, analyzing the characteristics of Alma’s architecture that make this possible. We can extend the system at different levels: at the input level, it is possible to adapt the system to a different language, modifying the front-end; at the output level, it is possible to change the animation detail, modifying the sampling frequency; also at the output level, it is possible to produce different pictures, modifying the visualizing rules; at a global level, it is possible to modify the input paradigm, changing the front-end and the back-end (rules and nodes).