Expert system
A third approach is to construct systems that are based on decision trees. Such systems are capable of learning, or of extending their knowledge base, using inductive reasoning. When the classification is done, the system uses a path through the tree. At the end, it arrives at a leaf, which indicates the class of solution to the problem.  Each bifurcation in the tree is based on an attribute, that is checked. The value of the attribute determines how to continue the path. Ideally, good results are obtained using small trees. The problem is finding good attributes to base the decisions on.