A snippet is a short document in which most occur only once, which makes conventional document comparison methods ineffective, such as the TF-IDF and cosine.

• 搜索引擎返回结果的摘要的特点在于文档长度短,大部分关键字最多只出现一次,因此传统文档比较方法所使用的TF-IDF、夹角余弦等方法对摘要比较失去了作用。