1. A pattern database building apparatus, comprising: a sentence analysis unit for segmenting an input corpus into example sentences with reference to a phrase dictionary and performing morpheme analysis and syntax analysis on the segmented example sentences; a hierarchy describing unit for describing hierarchy of the example sentences based on results of the morpheme analysis and the syntax analysis; a class transformation unit for performing class transformation on the example sentences, whose hierarchy has been described, with reference to a thesaurus/ontology and a classification rule dictionary; and a semantic representation pattern determination unit for marking optional expressions for the example sentences that have been undergone the class transformation, deleting meaningless expressions and additional information, converting the example sentences into their base form, deleting morphemic tags or symbols to determine a semantic representation pattern of the example sentences, and storing the determined semantic representation pattern in a database.