1. A processing logic modeling method for modeling a task, comprising: a decomposing step for decomposing said task into at least one level of sub-tasks; a tree structure forming step for forming a tree structure from said task and various levels of sub-tasks resulted from decomposing the task; and an annotating step for, according to the relations between the sub-tasks, annotating the nodes of the tree, thus obtaining a processing logic model for performing said task.