9. The video summarization method as claimed in claim 7 , wherein the relation between two root nodes, Relation child (α,β) is calculated by the following function: Relation type ⁡ ( I , J ) = ∑ I , J ⁢ ⁢ ident I , J the ⁢ ⁢ number ⁢ ⁢ of ⁢ ⁢ pairs where I and J represent the child nodes having the same classification type in the two concept expanding trees, ident I,J represents the number of the I and J child nodes having identical keywords, and the type is the classification type represented by who, where, when and what associated with child nodes.
7. The video summarization method as claimed in claim 3 , wherein calculating relations of all the bi-level trees is based on the following function: 
 Γ(α,β)=Relation root (α,β)×Relation child (α,β) where α and β represent two tuples, Relation root (α,β) represents the relation between two root nodes, Relation child (α,β) represents the relation between two sets of child nodes.