Document similarity refers to the degree of repetition between this paper and other papers. At present, there are two indicators, one is the similarity of full-text database, and the other is the similarity of self-built database.

Full-text database refers to all published papers, and the similarity of full-text database refers to the degree of repetition of this paper with all published papers.

Self-built library refers to the library built by all students' papers after the competition, and the similarity of self-built library is the degree of repetition of this paper with other students' papers.