I. Introduction
Artificial intelligence (AI) is one of the biggest technologies of the 21st century and has evolved from academic research to become one of the biggest drivers of business today. Recently, more and more countries have released a strategic plan for AI research. The AI field draws upon many research theories, including computer science, mathematics, psychology, linguistics, philosophy and so on. AI has been used to develop and advance many fields and industries, such as finance, healthcare, education, and transportation.