8. An instant messaging communication apparatus, comprising: a central processing unit; an input unit for inputting a first instant message and a first semantic tag for the instant message; a network module for transmitting the first input instant message with the first semantic tag encoded in one of a header and a tail of the first instant message, and receiving a second instant message with a second semantic tag encoded in one of a header and a tail of the second instant message; a construction unit for constructing a visual topic structural diagram of the transmitted and received first and second instant messages according to the first and second semantic tags; and a display unit for displaying the visual topic structural diagram.
8. An instant messaging communication apparatus, comprising: a central processing unit; an input unit for inputting a first instant message and a first semantic tag for the instant message; a network module for transmitting the first input instant message with the first semantic tag encoded in one of a header and a tail of the first instant message, and receiving a second instant message with a second semantic tag encoded in one of a header and a tail of the second instant message; a construction unit for constructing a visual topic structural diagram of the transmitted and received first and second instant messages according to the first and second semantic tags; and a display unit for displaying the visual topic structural diagram. 9. The apparatus according to claim 8 , further comprising: a storage unit for storing the transmitted and received first and second instant messages with semantic tags in a message log; the input unit further for selecting a semantic tag in a visual topic structural diagram; and a filter unit for filtering from the message log the instant message(s) associated with the selected semantic tag.