2. The method as recited in claim 1 , wherein determining the core geographical information in the document based on the scores of the plurality of geographical names comprises: computing aggregated scores for a plurality of geographical regions at a comparable or common level, each geographical region being related to at least one of the plurality of geographical names which are at the same or lower levels relative to the geographical region; identifying a highest scoring geographical region among the plurality of geographical regions; and taking a highest scoring geographical name in the highest scoring geographical region to be the core geographical information of the document.
2. The method as recited in claim 1 , wherein determining the core geographical information in the document based on the scores of the plurality of geographical names comprises: computing aggregated scores for a plurality of geographical regions at a comparable or common level, each geographical region being related to at least one of the plurality of geographical names which are at the same or lower levels relative to the geographical region; identifying a highest scoring geographical region among the plurality of geographical regions; and taking a highest scoring geographical name in the highest scoring geographical region to be the core geographical information of the document. 3. The method as recited in claim 2 , wherein the plurality of geographical regions are identified using a geographical information database containing a list of geographical names and hierarchical relationships among the list of geographical names, the list of geographical names including the plurality of geographical names in the document.