11. A system for web documents clustering, comprising: an inputting means for inputting a plurality of web documents; a collecting means for collecting link information and directory structure information of the inputted web documents; an extracting means for extracting, implemented by a processor, according to the collected link information and directory structure information, a hierarchical structure for the plurality of web documents; a revising means coupled between the extracting means and the outputting means for after extracting the hierarchical structure by the extracting means, revising the extracted hierarchical structure by analyzing the collected link information in the inputted web documents; and an outputting means for generating and outputting, based on the extracted hierarchical structure, plurality of clusters of the plurality of web documents, wherein the directory structure information is extracted by comparing directory paths of the web documents, wherein the directory paths include information about a location in a web server where each of the plurality of web documents are stored, and the extracted hierarchical structure corresponds to ancestor-descendent relationship structure of the plurality of web documents, wherein the plurality of web documents are grouped into the plurality of clusters according to the extracted hierarchical structure such that a first web document of the plurality of web documents and descendent web documents of the first web documents are grouped as a first cluster of the plurality of clusters, and a second web document of the plurality of web documents and descendent web documents of the second web documents are grouped as a second cluster of the plurality of clusters, and wherein the first and the second clusters have an ancestor-descendent relationship between each other corresponding to the extracted hierarchal structure.
12. The system according to claim 11 , wherein the outputting means also outputs hierarchical relationships of the generated web document clusters.