1. An information retrieval apparatus, comprising: an input unit for inputting characters; a database for storing a name, an attribute word associated with the name, and a degree of relevance indicating a degree of relevance between the name and the attribute word; a name retrieval unit for retrieving a name including the input characters from the database to output the retrieved name as a candidate name; an attribute word generating unit for extracting an attribute word associated with the candidate name output from the name retrieval unit from the database; and an output unit for displaying the attribute word extracted by the attribute word generating unit and the candidate name from the name retrieval unit, wherein: the attribute word generating unit is configured to: obtain a degree of relevance of the candidate name associated with the attribute word from the database with respect to a combination of the extracted attribute words; calculate a degree of independency indicating a degree of difference between the extracted attribute words; calculate a degree of coverage indicating an extent to which the combination of the extracted attribute words covers the candidate names; and calculate a degree of equality indicating uniformity of a number of corresponding candidate names for each attribute word; the attribute word generating unit comprises a first score calculating unit for calculating a score of the combination of the attribute words based on at least one of the calculated degree of independency, the calculated degree of coverage and the calculated degree of equality; and the attribute word generating unit outputs the combinations of the attribute words to the output unit in a descending order of the score.
5. The information retrieval apparatus according to claim 1 , wherein: the attribute words stored in the database are classified according to a type of the attribute word; and the attribute word generating unit calculates the score of the combination of the attribute words for each type of the attribute word, to output the combination of the attribute words having a maximum score to the output unit.