| 摘要 |
PROBLEM TO BE SOLVED: To suppress an increase of computation time and find an optimal solution of summarization stably.SOLUTION: An input unit 10 accepts an input document represented expressed as a tree structure, a score, length and an upper limit length L allowed as length of a summary. A ZDD construction unit 30 constructs ZDD representing a set of rooted subtrees of the tree structure. When a subtree in which the sum of scores becomes maximum is repeatedly calculated on the basis of the score and length of a node, the upper limit length L and the constructed ZDD, an optimal value calculation unit 32 calls the maximum value of the sum of scores of each node, stored in a storage unit, and recursively calculates a subtree in which the sum of scores of each node becomes maximum out of a rooted subtree in which the sum of length of each node is equal to length j out of a set of subtrees represented by ZDD with an LO side child node as a root node, and a rooted subtree including an HI side child node in which the sum of length of each node is equal to the length j out of a set of subtrees represented by ZDD with the n-th node as a root node.SELECTED DRAWING: Figure 1 |
