Vector Space Model(VSM) which is testified an better text denotation model is used in this paper.Criteria based on geometrical distance and post-test probability are introduced .

• 文本表示方面采用近年来应用较多且效果较好的向量空间模型(VSM),给出了基于几何距离的可分性判据和基于后验概率的可分性判据。