关键词: 认知, 机器学习, 等价, 约等价, 约简

Abstract: The knowledge acquisition of mankind usually takes advantage of the known knowledge to infer relevant unknown knowledge.Machine learning can resort to mankind’s process of knowledge acquisition.From the reverse process of learning，knowledge can be viewed as the start point of the learning processing to study and apply the results of cognitive learning.The known knowledge regarded as referential knowledge produces new knowledge through equivalent and approximate equivalent transformation.Approximate equivalent transformation includes expanding process and reduction process.Equivalent transformation processes knowledge of the same hierarchies.Expanding process of approximate equivalence produces detailed-level knowledge，and reduction process produces abstract-level knowledge.Instances analysis show that expanding and reduction algorithms have high accuracy for inferring new knowledge and can produce detailed and abstract level knowledge.

Key words: cognition, machine learning, equivalence, approximate equivalence, reduction