PURPOSE: A method, a system, and a computer-readable recording medium for dynamically providing an advertisement using collaborative filtering are provided to dynamically reconfigure user groups with a similar history, thereby immediately coping with a pattern change of a user. CONSTITUTION: A similarity calculator(230) obtains similarity between a specific user and another user based on at least one of a contents chain and a query chain. A user group manager(240) generates a user group based on the obtained similarity. The user group comprises a user whose similarity to the specific user is larger than a preset value. An advertisement pool manager(250) configures at least part of already provided advertisements as an advertisement pool.
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