2. The apparatus according to claim 1 , wherein the common keyword generation unit assigns the weight to the keyword in the document data according to the attribute of the keyword.
2. The apparatus according to claim 1 , wherein the common keyword generation unit assigns the weight to the keyword in the document data according to the attribute of the keyword. 3. The apparatus according to claim 2 , wherein the common keyword generation unit assigns the weight to the keyword according to a number of times the keyword appeared in the speech of the presentation.