Must is a graphical tracer for the Or-parallel Prolog language
Muse. Its purpose is to aid development and evaluation of Muse. The program can also
be used for demonstration purposes. Must runs under UNIX and X-windows. Our
goal was to make it simple to use but still expressive. This report will
describe the background, design and implementation of Must. It will be
concluded by an evaluation of the Must impact on the development of Muse
algorithms. The report will also include a description of Stat, a tool for
evaluating potential Or-parallelism in Prolog programs