In order to find useful information embedded in electronic form, efficient and effective techniques for large scale real text processing have become one of the most urgent demands.

• 文本过滤所研究的内容就是如何准确地表达用户需求，进而在大规模的信息流中自动地筛选出满足用户需求的信息，使人们更有效地利用信息资源。