Exercises

Extend the program by adding rules for the following family relationships (add more people if necessary, so that you can check your results):

brother(X, Y)	where X is Y's brother
sister(X, Y)	where X is Y's sister
son(X, Y)	where X is Y's son
daughter(X, Y)	where X is Y's daughter
married(X, Y)	where X is married to Y
ancestor(X, Y)	where X is Y's ancestor

What problems do you encounter? What is the nature of the problems? What solutions (if any) can you suggest. (Reading the literature on Prolog will help.)