Dempster-Shafer is actually a theory of combining evidence (
http://en.wikipedia.org/wiki/Dempster%E2%80%93Shafer_theory[
^]) not an "algorithm"
per se.
It can be used to
support an Expert System application, but it is not,
itself, an algorithm for problem solving reasoning as would be required for an Expert System.
You're going to need to define your problem-space, knowledge-representation, etc. before you even begin to think about coding an Expert System.