1. A computer-implemented 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 annotating nodes of the tree structure, the annotating representing execution instructions annotated at a first node of the tree structure with respect to executing the execution instructions at a second node of the tree structure wherein the first and second nodes are at different levels of the tree structure, thus obtaining a processing logic model for performing said task.