Decision Trees

Synonyms

Classification trees

Definition

Decision trees are compact tree like representations of conditions that specify when a decision should be applied together with the actions/decision. Decision trees consist into intermediate nodes and leaf nodes. The outgoing edges from intermediate nodes are labeled by conditions. The leaf nodes are labeled by decisions or actions. The way decision trees are used is by starting at the root then navigating down on true conditions until a leaf is reached. The action or decision in the leaf is then taken. Decision trees are just a compact representation of decision rules: the condition under which an action is taken is the conjunction of conditions starting at the root of the decision tree and leading to the leaf labeled by the action. An example of a decision tree is given in Fig. 1.

Decision Trees. Figure 1

Example of a decision tree for selecting a database.