When a retrieval condition including a first desired word and a first desired
component including a value in which the first desired word is included, is inputted,
a first detecting device detects second desired components each being similar to
the first desired component, an acquiring device acquirers second desired words
each being similar to the first desired word, a first retrieving device retrieves
first structured documents each including a first component including a value in
which one of the first desired word and the second desired words is included, a
second retrieving device retrieves second structured documents each including a
second component corresponding to one of the first desired component and the second
desired components and including or corresponding to the first component.
