 A somewhat different DAG @-@ based formulation of scheduling constraints is used by the program evaluation and review technique ( <unk> ) , a method for management of large human projects that was one of the first applications of DAGs . In this method , the vertices of a DAG represent milestones of a project rather than specific tasks to be performed . Instead , a task or activity is represented by an edge of a DAG , connecting two milestones that mark the beginning and completion of the task . Each such edge is labeled with an estimate for the amount of time that it will take a team of workers to perform the task . The longest path in this DAG represents the critical path of the project , the one that controls the total time for the project . Individual milestones can be scheduled according to the lengths of the longest paths ending at their vertices . 
