Visualization/animation of programs in Alma: obtaining different results

Alma, a system for program animation, 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. The back-end of this system works over an execution tree (DAST - decorated abstract syntax tree), 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). In this paper, the main goal will be to present the extensibility of the system in the sense of adding or modifying inputs and outputs. We also discuss the characteristics of Alma's architecture that make this possible.