4. A method as recited in claim 1 , rewriting the input keyword comprises: labeling a respective importance value for each word included in the input keyword; and deleting one or more words whose respective importance values are lower than a preset importance value threshold from the input keyword.
4. A method as recited in claim 1 , rewriting the input keyword comprises: labeling a respective importance value for each word included in the input keyword; and deleting one or more words whose respective importance values are lower than a preset importance value threshold from the input keyword. 5. A method as recited in claim 4 , wherein the respective importance value for each word included in the input keyword is labeled based on one or more of a respective syntax, grammar, semantics, or statistical characteristic of a respective word.