1. A computer-implemented method for automatically updating a tag embedded in a webpage that summarizes a current version of the webpage, the method comprising: extracting, by a computing device, a first model representative of the current version of the webpage, the first model including nodes defining a hierarchy of elements of the current version of the webpage; comparing, by the computing device, the first model with a second model corresponding to a previous version of the webpage to detect one or more changes to the webpage; determining by the computing device, at least one keyword corresponding to the current version of the webpage if the changes exceed a threshold, wherein determining the keyword comprises: extracting an item set of words or phrases from the current version of the webpage; selecting a rule from a trained set of rules based on the item set of extracted words or phrases, the rule defining (1) an association of the item set to a keyword and (2) a property vector that measures quality of the association; and computing a maximum likelihood score based on the property vector corresponding to the selected rule, the maximum likelihood score representing a probability of relationship between the selected rule and the corresponding keyword; comparing, by the computing device, the keyword corresponding to the current version of the webpage with at least one keyword corresponding to the previous version of the webpage; and updating, by the computing device, the tag of the webpage to include the keyword corresponding to the current version depending on the comparison and the likelihood score.