ETRI-KEMONG SET [12] is used as the test collection.
This test collection is an encyclopedia for students published
by KeMong Co., which consists of 23,113 entries with
respective explanations. The average number of the terms in
the explanation is 56. The total number of natural language
queries is 45 and the average number of terms in the queries
is three. The average number of the relative documents per
query is nine. Table 6 describes the statistics of the test
collection.