There has been a significant amount of research into debugging of logic and constraint logic programming languages. In particular, this research has resulted in several sophisticated visual debugging tools such as the Transparent Prolog Machine (TPM) developed for Prolog, Explorer developed for Oz, APT developed for CIAO, and the Execution Tree Viewer (ETV) developed for Prolog IV. However, the picture is far from perfect, and in practice most LP programmers use simple textual debuggers (also called tracers) little better than those provided twenty years ago. The aim of this project is to design and implement ViMer, a visual debugging environment for Mercury programs which satisfies the following requirements. First, it should support a new execution tree representation which provides a better way of visualizing backtracking in AND-OR-like trees. Second, it should use incremental constraint-solving to efficiently draw and incrementally update the visualization of the execution tree. And finally, it must borrow techniques from standard tracers (such as the use of spy points to reduce the amount of tree nodes, and the placement of restrictions on the amount of information stored at each node) that help keep the tool efficient while still providing enough information for debugging.

The results of this project are published in:

ViMer: a visual debugger for Mercury M. Cameron, M. Garcia de la Banda, K. Marriott, and P. Moulder. In proceedings of the Fifth ACM-SIGPLAN International Conference on Principles and Practice of Declarative Programming, 2003. In Print.
 
Core Reference
P. Deransart, M. Hermenegildo and J. Maluszynski. Analysis and Visualization Tools for Constraint Programming: Constraint Debugging. Lecture Notes in Computer Science, 1870, Springer Verlag, 2000.

R. Vaupel, E. Pontelli and G. Gupta. Visualization of And/Or-Parallel Execution of Logic Programs. In L. Naish (Ed.), Proceedings of the 14th International Conference on Logic Programming, Cambridge, 271-285. MIT Press, July 8-11, 1997.
 
Student
Michael Cameron
 
Supervisor
Marica Garcia de la Banda
David Jeffrey
Kim Marriott
 
Type
Bachelor Computer Science (Honours)
 
Project Start
February 2001
 
Completion
November 2001