OKapi BM25 算法介绍
From wikipedia.org英文版,我主要将其改变成中文。
BM25(Best Match25)是在信息检索系统中根据提出的query对document进行评分的算法。It is based on the probabilistic retrieval framework developed in the 1970s and 1980s by Stephen E. Robertson, Karen Spärck Jones, and others.BM25算法首先由OKapi系统实现,所以又称为OKapi BM25。
BM25属于bag-of-words模型,bag-of-words模型只考虑document中词频,不考虑句子结构或者语法关系之类,把document当做装words的袋子,具体袋子里面可以是杂乱无章的。It is not a single function, but actually a whole family of scoring functions, with slightly different components and parameters. One of the most prominent instantiations of the function is as follows.
对于一个query , 包括关键字 , 一个文档的BM25得分: