然而，韩礼德理论也存在一定的不足。
However, in Halliday's theory, there are certain inadequacies.
目前常用的几种间隙模型都存在一定的不足，不完全符合实际运动。
These kinds of passing model can not exactly coincide with the actual motion.
虽然目前某些系统已采用一些技术进行反垃圾邮件，但这些技术都存在一定的不足。
Although some current systems have adopted some techniques to proceed Anti-Spam, these techniques have some shortages.
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