Positive examples and counterexamples are used together. A positive example, also known as a positive example, refers to an example that contains the essential characteristics and internal relations of concepts or rules; Counterexample, also known as counterexample, refers to an example that does not contain or only contains a small part of the main attributes and key features of a concept or rule. Generally speaking, the positive examples of concepts or rules convey the information that is most beneficial to generalization, and the negative examples convey the information that is most beneficial to discrimination.