THE OVERALL OBJECTIVE OF AN ASSEMBLY WORK CELL IS THE EFFECTIVE COMPLETION OF THE ASSIGNED TASKS. TO ACHIEVE THIS OBJECTIVE, THE MACHINES IN THE WORKCELL ARE VIEWED AS A TEAM WORKING IN COOPERATION WITH EACH OTHER. TO CAPTURE THE FLEXIBILITY PROVIDED BY SUCH COOPERATION, THREE TASK COOPERATION MODES ARE DEFINED: MANDATORY, OPTIONAL, AND CONCURRENT. THE DYNAMIC PLANNING PROBLEM IS DIVIDED INTO TWO PARTS: COOPERATION REQUIREMENTS PLANNING TO DETERMINE A CURRENTLY FEASIBLE SET OF MACHINES THAT CAN COMPLETE A TASK; AND TASK ASSIGNMENT AND EXECUTION PLANNING TO ASSIGN THE TASK TO A SINGLE MACHINE OR SET OF MACHINES FROM THE FEASIBLE SET.