A method of geographical name extraction from Japanese text for thematic geographical search

摘要

A text retrieval method called the thematic geographical search method has been developed and applied to a Japanese encyclopedia called the World Encyclopaedia. In this method, the user specifies a search theme using free words, then obtains a sorted list of excerpts and hyperlinks to encyclopedia sentences that contain geographical names. Using this list, the user can also open maps that indicate the locations of the names. To generate an index of names for this searching, a method of extracting geographical names has been developed. In this method, geographical names are extracted, matched to names in a geographical name database, and identified. Geographical names, however, often have several types of ambiguities. Ambiguities are resolved by using non-local context analysis, which uses a stack and several other techniques. As a result, the precision of extracted names is more than 96% on average. This method depends on features of the Japanese language, but the strategy and most of the techniques can be applied to texts in English or other languages.